Separations

16 pages, 3820 KiB

Open AccessEditor’s ChoiceArticle

Simple Green Purification of Spilanthol from Natural Deep Eutectic Solvent and Ethanolic Acmella oleracea (L.) R.K. Jansen Extracts Using Solid-Phase Extraction

by Fabian Alperth, Sebastian Erhart, Olaf Kunert and Franz Bucar

Separations 2024, 11(8), 251; https://doi.org/10.3390/separations11080251 - 20 Aug 2024

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Abstract

Spilanthol is a major N-alkylamide constituent of Acmella oleracea (L.) R.K. Jansen with diverse pharmacological properties. We recently showed the applicability of NADES (natural deep eutectic solvents) for the green extraction of spilanthol. However, the purification of targets from NADES poses a [...] Read more.

Spilanthol is a major N-alkylamide constituent of Acmella oleracea (L.) R.K. Jansen with diverse pharmacological properties. We recently showed the applicability of NADES (natural deep eutectic solvents) for the green extraction of spilanthol. However, the purification of targets from NADES poses a challenging step due to their non-volatility. A simple green method to retrieve spilanthol with minimal instrumental effort was devised, fractioning NADES (choline chloride/methylurea, choline chloride/1,2-propanediol, choline chloride/citric acid) and dry ethanolic extracts by SPE on C18 material, eluting merely with ethanolic solutions. The relative distribution of spilanthol and organic adulteration in SPE fractions were detected by HPLC-DAD, followed by scale-up, quantification and purity determination in an NMR-based approach. Isocratic elution with 52% ethanol (v/v) proved suitable in all experiments. The three purest 10 mL fractions combined yielded 12.21 mg spilanthol at 71.65% purity from NADES extract ChCl/P (choline chloride/1,2-propanediol, molar ratio 1:2, +20% m/m water). Ethanolic extract samples showed purities ranging from 77.27 to 80.27% in combined raw fractions. For all samples, purity increased by removing non-soluble substances from organic solutions. Pooled NADES extract fractions showed 89.71% in final samples, ethanolic extracts 87.25 to 91.93%. The highest purities of individual fractions per extract were 89.23 to 94.15%. This cheap and simple purification process is promising to acquire spilanthol for research purposes or as a sample preparation step before HPLC on a semi-preparative to preparative scale, as the substance is highly priced and scarcely available on the market. Organic solvents can be reused, and preliminary scale-up possibilities are shown. Full article

(This article belongs to the Special Issue Extraction and Analysis of Chemical Compositions of Natural Products and Plants)

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16 pages, 1297 KiB

Open AccessEditor’s ChoiceArticle

Polyphenols Extraction from Different Grape Pomaces Using Natural Deep Eutectic Solvents

by Alessandro Frontini, Andrea Luvisi, Carmine Negro, Massimiliano Apollonio, Rita Accogli, Mariarosaria De Pascali and Luigi De Bellis

Separations 2024, 11(8), 241; https://doi.org/10.3390/separations11080241 - 8 Aug 2024

Viewed by 1244

Abstract

Exploiting by-products from the oenological industry to extract antioxidant chemicals is a shared goal that combines the need to reduce the wine sector’s environmental impact with the need to improve the availability of these biomolecules, according to a circular economy approach. Natural deep [...] Read more.

Exploiting by-products from the oenological industry to extract antioxidant chemicals is a shared goal that combines the need to reduce the wine sector’s environmental impact with the need to improve the availability of these biomolecules, according to a circular economy approach. Natural deep eutectic solvents (NaDES) have recently captured researchers’ interest as a safer and more environmentally friendly alternative to traditional solvents due to their effectiveness, low toxicity, and stability. In this work, we set out to investigate several NaDES for the extraction of phenolic chemicals from local monovarietal grape pomace resulting from different vinification procedures (including both red and rosé vinification of Negroamaro and Primitivo grapes; rosé vinification of Susumaniello grapes and white vinification of Chardonnay, Fiano and Malvasia bianca grapes), with the additional goal of generalizing the use of NaDES to extract chemicals of interest from organisms selected from the wide plant biodiversity. Three binary choline chloride-based NaDES (DES-Lac, DES-Tar, and DES-Gly, with lactic acid, tartaric acid, and glycerol as hydrogen bond donors, respectively) were compared to ethanol as a conventional solvent, and the extracts were evaluated using HPLC/MS and colorimetric techniques. The results revealed that each NaDES produces a substantially higher total phenolic yield than ethanol (up to 127.8 mg/g DW from Primitivo rosé grape pomace). DES-Lac and DES-Tar were more effective for anthocyanins extraction; the most abundant compound was malvidin 3-O-glucoside (highest extraction yield with DES-Lac from Susumaniello pomace: 29.4 mg/g DW). Regarding phenolic compounds, DES-Gly was the most effective NaDES producing results comparable to ethanol. Unexpectedly, Chardonnay pomace has the greatest content of astilbin. In most cases, grape pomace extracts obtained by rosé and white vinification provided the maximum yield. As a result, NaDES have emerged as a viable alternative to traditional organic solvent extraction techniques, allowing for higher (or equal) yields while significantly lowering costs, hazards, and environmental impact. Full article

(This article belongs to the Special Issue Extraction and Characterization of Bioactive Compounds from Plant and Natural Sources)

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12 pages, 1288 KiB

Open AccessEditor’s ChoiceArticle

Evolution of Eight Biogenic Amines in Raw and Preserved Mackerel (Scomber scombrus) Fillets Monitored by UHPLC-PDA

by Laura Barp, Erica Moret and Sabrina Moret

Separations 2024, 11(8), 235; https://doi.org/10.3390/separations11080235 - 1 Aug 2024

Viewed by 599

Abstract

The presence of biogenic amines (BAs) in seafood can pose a health risk to consumers, as they have been linked to adverse reactions such as histamine poisoning. Although the only biogenic amine for which maximum limits have been set is histamine, it is [...] Read more.

The presence of biogenic amines (BAs) in seafood can pose a health risk to consumers, as they have been linked to adverse reactions such as histamine poisoning. Although the only biogenic amine for which maximum limits have been set is histamine, it is also important to regulate the presence of other amines associated with certain adverse effects. In this study, the official method for determining histamine was slightly modified and adapted for a UHPLC-PDA system and applied to analyze raw and preserved mackerel fillet samples. The evolution of biogenic amines during the storage period under refrigerated conditions revealed that, within two days, the limit for the content of histidine of 100 mg/kg was exceeded in raw fillets, while the histidine content in preserved mackerel (in oil and marinated) remained more stable. The thawing phase, whether in the fridge or at room temperature, did not significantly affect the BA content. Additionally, three different cooking methods (steaming, oven-baking, and boiling) significantly decrease the levels of BAs in highly contaminated raw mackerel fillets. Full article

(This article belongs to the Special Issue Determination of Potentially Toxic Elements in Food, Beverage and Medicinal Plants by Analytical Methods and Separation Technologies)

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16 pages, 5889 KiB

Open AccessEditor’s ChoiceArticle

LC-MS/MS-QTOF Identification of Phenolic Compounds of Sideritis Species Cultivated in Greece

by Eleftheria H. Kaparakou, Charalabos D. Kanakis, Maroula G. Kokotou, Georgios Papadopoulos and Petros A. Tarantilis

Separations 2024, 11(8), 229; https://doi.org/10.3390/separations11080229 - 26 Jul 2024

Viewed by 1951

Abstract

Phenolic compounds are plant secondary metabolites, one of the most common and widespread groups of substances in plants, as well as a major group of phytochemicals present in medicinal and aromatic plants. The phytochemical composition of the hydroalcoholic extracts from S. raeseri, [...] Read more.

Phenolic compounds are plant secondary metabolites, one of the most common and widespread groups of substances in plants, as well as a major group of phytochemicals present in medicinal and aromatic plants. The phytochemical composition of the hydroalcoholic extracts from S. raeseri, S. scardica and S. syriaca was determined by LC-MS/MS-QTOF analysis. A total amount of 23 secondary metabolites were identified, including 17 flavonoids (Fs), 4 phenylethanoid glycosides (PEGs), 1 phenolic acid (PA) and 1 fatty acid (FA). Among the three species, the constituents that have been detected in all of nine samples were: verbascocide/isoverbascoside (PEG), apigenin 7-O- glucoside (F), isoscutellarein 7-O-[6″-O-acetyl]-allosyl(1→2)-glucoside (F) and apigenin 7-(4″-p-coumaroylglucoside) (F). This study contributes to the phytochemical characterization of the Sideritis spp. by providing a comparative study of bioactive compounds present in three different Sideritis species, S. raeseri, S. scardica and S. syriaca, which are widely used as a herbal medicine in Mediterranean region and Balkan Peninsula. Full article

(This article belongs to the Special Issue Isolation and Identification of Biologically Active Natural Compounds)

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25 pages, 5094 KiB

Open AccessEditor’s ChoiceArticle

Extraction of Bioactive Compound-Rich Essential Oil from Cistus ladanifer L. by Microwave-Assisted Hydrodistillation: GC-MS Characterization, In Vitro Pharmacological Activities, and Molecular Docking

by Naoufal El Hachlafi, Fahd Kandsi, Amine Elbouzidi, Fatima Zahra Lafdil, Ghizlane Nouioura, Emad M. Abdallah, Rhizlan Abdnim, Mohamed Bnouham, Samiah Hamad Al-Mijalli, Hanae Naceiri Mrabti and Kawtar Fikri-Benbrahim

Separations 2024, 11(7), 199; https://doi.org/10.3390/separations11070199 - 27 Jun 2024

Cited by 2 | Viewed by 1494

Abstract

Cistus ladanifer L. is an aromatic and resinous perennial shrub commonly used in Moroccan folk medicine against a range of illnesses including skin problems, diabetes, diarrhea, and inflammation. The current investigation aims to determine the bioactive compounds of C. ladanifer essential oil (CL-Eo) [...] Read more.

Cistus ladanifer L. is an aromatic and resinous perennial shrub commonly used in Moroccan folk medicine against a range of illnesses including skin problems, diabetes, diarrhea, and inflammation. The current investigation aims to determine the bioactive compounds of C. ladanifer essential oil (CL-Eo) extracted by microwave-assisted hydrodistillation and their biological properties using in vitro and molecular docking approaches. The GC-MS analysis identified linderol (17.76%), gamma-terpinene (17.55%), and borneol (13.78%) as main bioactive compounds. CL-Eo significantly inhibited α-amylase (IC₅₀ = 0.41 ± 0.009 mg/mL), α-glucosidase (IC₅₀ = 0.49 ± 0.002 mg/mL) and lipase (IC₅₀ = 0.45 ± 0.004 mg/mL) enzymes. Moreover, CL-Eo showed significant hemoglobin glycation as well as antioxidant capacity as indicated by DPPH, ABTS, Frap and beta-carotene tests. The antimicrobial evaluation used disc-diffusion and microdilution tests in vitro. The results showed that CL-Eo had significant antibacterial activity, particularly against P. mirabilis (17.16 ± 1.04 mm), and moderate effects against L. innocua (13.48 ± 1.65 mm) and E. coli (12.47 ± 0.61 mm). In addition, it demonstrated potent antifungal activity against C. albicans (18.01 ± 0.91 mm) and C. tropicalis (16.45 ± 0.32 mm). The MIC and MBC tests provided confirmation that CL-Eo exhibited potent growth inhibition. The MIC ranged from 0.25 to 8.0% v/v and the MBC or MFC ranged from 0.25 to 16.0% v/v Eo. The tolerance level ratio showed bactericidal and fungicidal effects against tested microbial strains in varying degrees. According to these data, CL-Eo might be suggested as a promising candidate for drug development, specifically for combating candidiasis and diabetes. Full article

(This article belongs to the Special Issue Extraction, Purification and Application of Bioactive Compounds)

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11 pages, 1398 KiB

Open AccessEditor’s ChoiceArticle

A Novel Solvent Microextraction Lab-in-Syringe System Coupled with Atomic Absorption Spectrometry for Thallium Determination in Water Samples

by Arina Skok, Natalia Manousi, Yaroslav Bazel, Andriy Vishnikin and Aristidis Anthemidis

Separations 2024, 11(7), 193; https://doi.org/10.3390/separations11070193 - 21 Jun 2024

Viewed by 956

Abstract

Thallium is an accumulative highly toxic metal, that can be present in environmental samples due to industrial pollution and is dangerous for living organisms. Thus, its determination at trace levels is necessary. The lab-in-syringe (LIS) is considered to be a simple, functional, and [...] Read more.

Thallium is an accumulative highly toxic metal, that can be present in environmental samples due to industrial pollution and is dangerous for living organisms. Thus, its determination at trace levels is necessary. The lab-in-syringe (LIS) is considered to be a simple, functional, and versatile, technique that combines operational concepts and flow and sequential injection analysis. In this study, a liquid-phase microextraction LIS system was developed as a front-end to flame atomic absorption spectrometry (FAAS) for the determination of thallium in water samples. The proposed approach is based on the formation of Tl(III) ammonium–pyrrolidine–dithiocarbamate complex followed by its extraction using di-isobutyl-ketone. These procedures take place within the syringe barrel of the LIS system. The limit of detection of the developed method was 2.1 µg L⁻¹ with a linear range from 7.0 to 400 µg L⁻¹. The relative standard deviation (RSD) was 3.9% (at 50.0 µg L⁻¹ Tl(I)), demonstrating good precision. Moreover, good method accuracy was obtained since the relative recovery values were within the range of 93.4–101.2%. Finally, reliable method applicability and green merits were demonstrated using the blue applicability grade index and green analytical procedure index, respectively. The proposed method was used for the analysis of environmental water samples. Full article

(This article belongs to the Section Purification Technology)

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16 pages, 804 KiB

Open AccessEditor’s ChoiceArticle

Simultaneous Determination of Multiresidues of Pesticides and Veterinary Drugs in Agricultural Soil Using QuEChERS and UHPLC–MS/MS

by Michele C. Vicari, Janice F. Facco, Sandra C. Peixoto, Gabriel S. de Carvalho, Luana Floriano, Osmar D. Prestes, Martha B. Adaime and Renato Zanella

Separations 2024, 11(6), 188; https://doi.org/10.3390/separations11060188 - 14 Jun 2024

Cited by 1 | Viewed by 1002

Abstract

Soil is one of the main destinations for pesticides and veterinary drugs used in agriculture and animal production. The negative consequences of the accumulation of these compounds in the environment make it important to monitor these compounds in the soil. In this study, [...] Read more.

Soil is one of the main destinations for pesticides and veterinary drugs used in agriculture and animal production. The negative consequences of the accumulation of these compounds in the environment make it important to monitor these compounds in the soil. In this study, we compared different extraction procedures using solvent shaking, ultrasound, or QuEChERS, and their combinations, for the simultaneous determination of 75 pesticide and seven veterinary drug residues in agricultural soil by ultra-high performance liquid chromatography coupled to serial mass spectrometry (UHPLC–MS/MS). The method using QuEChERS combined with shaking showed the best results for soil using the addition of water, followed by extraction with acetonitrile acidified with acetic acid and shaking in a shaker. For partitioning, anhydrous magnesium sulfate and anhydrous sodium acetate were used. The extract was centrifuged, filtered, and diluted (1:4, v/v) in water for determination by UHPLC–MS/MS. Method validation showed adequate accuracy and precision results, with recoveries between 70 and 120% and RSD ≤ 20% for the vast majority of the compounds evaluated at the spike levels of 10, 25, 50, and 100 μg kg⁻¹. The method limits of detection (LOD) and quantification (LOQ) ranged from 3.0 to 7.5 μg kg⁻¹ and from 10 to 25 μg kg⁻¹, respectively. The method was applied to different agricultural soil samples and proved to be efficient for routine analysis. Full article

(This article belongs to the Collection Feature Paper Collection in Section 'Environmental Separations')

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15 pages, 7166 KiB

Open AccessEditor’s ChoiceArticle

The Pollution Characteristics and Fate of Microplastics in Typical Wastewater Treatment Systems in Northern China

by Yi Ma, Zhenkang Bao, Shangying Cai, Qiong Wang, Beibei Dou, Xiangyu Niu, Qingzhen Meng, Penghao Li and Xiaoying Guo

Separations 2024, 11(6), 177; https://doi.org/10.3390/separations11060177 - 6 Jun 2024

Cited by 1 | Viewed by 1015

Abstract

This study focuses on the occurrence status and removal efficiency of microplastics in wastewater treatment plant processes. Analysis of effluent and sludge samples from the Wulongkou and Shuangqiao wastewater treatment plants in Zhengzhou revealed an overall microplastic removal efficiency of 95.64% and 92.53%, [...] Read more.

This study focuses on the occurrence status and removal efficiency of microplastics in wastewater treatment plant processes. Analysis of effluent and sludge samples from the Wulongkou and Shuangqiao wastewater treatment plants in Zhengzhou revealed an overall microplastic removal efficiency of 95.64% and 92.53%, respectively, indicating the effectiveness of wastewater treatment plants in reducing microplastic emissions. Microplastics primarily exist in forms such as fiber, fragment, floc, film, and grain. Fibers are predominant in the effluent of the Wulongkou plant, while fibers and films predominate in the effluent of the Shuangqiao plant. Moreover, microplastics are predominantly sized below 500 μm, with larger microplastics (2–5 mm) exhibiting higher removal efficiencies after secondary treatment. Analysis of microplastic types revealed that PE is the most common type in the effluent of the Wulongkou plant, while the Shuangqiao plant predominantly contains PE and PA66. The abundance of microplastics in sludge samples was found to be 6.4 ± 0.8 items/g and 11.3 ± 2.3 items/g, highlighting sludge as an important sink for microplastics. Surface analysis of microplastics revealed characteristics such as wrinkles and cracks, with energy-dispersive spectroscopy indicating significant adsorption of heavy metal elements such as Zn, Hg, and Pb onto microplastic surfaces in sludge. These findings underscore the importance of microplastic removal in wastewater treatment processes and provide scientific evidence for the control and management of microplastic pollution in the future. Full article

(This article belongs to the Special Issue Adsorption and Remediation of Emerging Pollutants from Water and Soil)

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14 pages, 3318 KiB

Open AccessEditor’s ChoiceArticle

Hyphenation of Thermodesorption into GC × GC-TOFMS for Odorous Molecule Detection in Car Materials: Column Sets and Adaptation of Second Column Dimensions to TD Pressure Constraints

by Romain Klein, José Dugay, Jérôme Vial, Didier Thiébaut, Guy Colombet, Donatien Barreteau and Guillaume Gruntz

Separations 2024, 11(6), 162; https://doi.org/10.3390/separations11060162 - 23 May 2024

Viewed by 782

Abstract

Vehicle interior air quality is an issue of growing interest among car manufacturers and customers. GC-MS is the benchmark method for the analysis of indoor air or material emissions. It is suitable for the quantification of target pollutants and the most abundant compounds. [...] Read more.

Vehicle interior air quality is an issue of growing interest among car manufacturers and customers. GC-MS is the benchmark method for the analysis of indoor air or material emissions. It is suitable for the quantification of target pollutants and the most abundant compounds. It fails, however, to uncover the true molecular complexity of these samples. In the present study, we describe the development of a TD-GC × GC-TOFMS method designed to detect polar and potentially odorous molecules in car material emissions. Attention is paid to the hyphenation of the thermodesorber and the gas chromatograph, both at software and hardware levels, and the constraints due to pressure limitations on the thermodesorber (evaluated at 414 kPa/60 psi at the end of the temperature ramp and at 138 kPa/20 psi at rest). A compromise was made for the 2D column length and diameter to balance separation and pressure (50 × 0.18 × 0.18 cm × mm × µm + 60 cm transfer line selected). On various materials, we were able to observe several hundreds of polar molecules, among them were between 75 and 150 odorants per material. This work lays the foundation for the widespread screening of potential odorants in car material emissions. Full article

(This article belongs to the Collection Feature Paper Collection in Section Chromatographic Separations)

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20 pages, 739 KiB

Open AccessEditor’s ChoiceReview

Research Progress in the Separation of Chemical Components from Essential Oils by High-Speed Countercurrent Chromatography

by Linhong He, Zihao Zhong, Lijuan Zhang and Xi Bai

Separations 2024, 11(5), 152; https://doi.org/10.3390/separations11050152 - 15 May 2024

Viewed by 1534

Abstract

Essential oils (EOs) are vital secondary metabolites in plants. They have garnered substantial attention owing to their distinct flavors and desirable attributes, including potent antioxidant, antibacterial, and antitumor properties. Nevertheless, the active constituents of EOs exhibit intricate chemical structures, and conventional separation techniques [...] Read more.

Essential oils (EOs) are vital secondary metabolites in plants. They have garnered substantial attention owing to their distinct flavors and desirable attributes, including potent antioxidant, antibacterial, and antitumor properties. Nevertheless, the active constituents of EOs exhibit intricate chemical structures, and conventional separation techniques are inadequate for purifying the individual chemical components from EOs. High-speed countercurrent chromatography, based on the principles of a hydrodynamic equilibrium system, has emerged as a liquid–liquid chromatographic separation method renowned for its ability to handle substantial single injection volumes and the absence of irreversible adsorption. Consequently, in recent years, this technique has been widely employed in the isolation and refinement of natural products. In this review, a comprehensive analysis is conducted, contrasting the merits and demerits of high-speed countercurrent chromatography with conventional separation methods. The solvent systems, elution modes, commonly employed detectors, and practical applications are reviewed in the context of high-speed countercurrent chromatography for essential oil separation and purification. Furthermore, this review offers a glimpse into the potential prospects of applying this technique, with the intention of serving as a valuable reference for the use of high-speed countercurrent chromatography in the purification of EOs. Full article

(This article belongs to the Special Issue HPLC or Other Chromatographic-Based Methods for Analysis of Bioactive Compounds in Plant, Food, and Pharmaceutical Products)

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17 pages, 9132 KiB

Open AccessEditor’s ChoiceArticle

Aluminum Removal from Rare Earth Chloride Solution through Regulated Hydrolysis via Electrochemical Method

by Yaoyao Zhu, Jian Li, Dongyue Xie, Hui Zhang, Man Li, Binfeng Xu, Xuxia Zhang, Yangyang Xie and Tao Qi

Separations 2024, 11(5), 149; https://doi.org/10.3390/separations11050149 - 12 May 2024

Viewed by 1662

Abstract

Due to the coexistence of Al³⁺ and RE³⁺ and their similar properties, the separation of aluminum from rare earths is difficult. In this study, selective precipitation was used to separate aluminum from rare earth chloride solution via electrochemical regulated hydrolysis. By [...] Read more.

Due to the coexistence of Al³⁺ and RE³⁺ and their similar properties, the separation of aluminum from rare earths is difficult. In this study, selective precipitation was used to separate aluminum from rare earth chloride solution via electrochemical regulated hydrolysis. By controlling the current density and electrolytic time, the rate of hydroxyl ion production was regulated, and the selective separation of rare earth and aluminum was realized according to the different precipitation sequences. By altering the temperature, current density, pH value, and other parameters, the separation performance of aluminum from rare earth in mixed rare earth chloride systems was systematically investigated. The removal rate of aluminum reached 88.35%, and the loss rate of rare earth was only 5.99% under optimized conditions. Compared with traditional neutralization hydrolysis, the new process showed higher efficiency and lower rare earth loss rate. Furthermore, a kinetic analysis of aluminum precipitation revealed that the reaction adhered to pseudo-first order kinetics. Additionally, the precipitate obtained via separation and filtration was amorphous alumina hydroxide with a small amount of rare earth attached. No reagent was consumed for the new process, which was more efficient and cleaner, providing a new idea for removing aluminum impurities from rare earth solutions. Full article

(This article belongs to the Section Purification Technology)

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24 pages, 10774 KiB

Open AccessEditor’s ChoiceReview

Achievements in Preparation of Cyclodextrin–Based Porous Materials for Removal of Pollutants

by Kaiyue Bao, Anyun Zhang, Yiyao Cao and Lei Xu

Separations 2024, 11(5), 143; https://doi.org/10.3390/separations11050143 - 7 May 2024

Viewed by 1185

Abstract

Cyclodextrin–based porous materials have been widely applied in removing various organic pollutants from water environments, due to their unique physical and chemical properties, like the size–matching effect and hydrophobic interaction. Large numbers of hydroxyl groups in its external structure give cyclodextrin a high [...] Read more.

Cyclodextrin–based porous materials have been widely applied in removing various organic pollutants from water environments, due to their unique physical and chemical properties, like the size–matching effect and hydrophobic interaction. Large numbers of hydroxyl groups in its external structure give cyclodextrin a high solubility in water, but the existence of these hydroxyl groups also endows cyclodextrin with the ability to be chemically modified with various functional groups to reduce its solubility in water and, meanwhile, to develop some novel functionalized cyclodextrin–based porous materials for selective removal of the target organic pollutants. This review focuses on the recent development in the synthesis of cyclodextrin–based porous materials (crosslinked cyclodextrin polymers and immobilized cyclodextrins), as well as highlighting their applications and mechanisms in the removal of dyes, endocrine disruptors, and mixed pollutants from water. Finally, the challenges and future perspectives in related research fields are discussed. Full article

(This article belongs to the Special Issue Adsorption and Remediation of Emerging Pollutants from Water and Soil)

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18 pages, 8322 KiB

Open AccessEditor’s ChoiceArticle

Decoding the Volatile Profile of White Romanian Fetească Wines

by Fulvia-Ancuța Manolache, Denisa-Eglantina Duță, Gabriela Daniela Criveanu-Stamatie, Teodora-Alexandra Iordache and Maria-Cristina Todașcă

Separations 2024, 11(5), 141; https://doi.org/10.3390/separations11050141 - 3 May 2024

Cited by 1 | Viewed by 1172

Abstract

The wine’s volatilome, most of the time, defines not only its aroma, but also, its major attributes. In the case of wines, the authentication process has become imperative, in light of increased production of alcoholic beverages; consequently, reliable analytical methods have served for [...] Read more.

The wine’s volatilome, most of the time, defines not only its aroma, but also, its major attributes. In the case of wines, the authentication process has become imperative, in light of increased production of alcoholic beverages; consequently, reliable analytical methods have served for it. Therefore, the goal of this research was to establish the global volatile profile of traditional Romanian white wines from Fetească varieties (Fetească albă, Fetească regală) in order to identify its unique characteristics by means of a headspace solid-phase microextraction coupled with gas chromatography analysis (HS-SPME/GC-MS) and e-Nose devoted techniques. Statistics was also employed aimed at differentiating the analyzed wine by varietal groups. Consequently, 23 volatile compounds were detected and quantified in 39 Fetească white wine samples originating from various production areas (Muntenia, Oltenia, Transylvania, Banat and Dobrogea), then further classified according to their odor thresholds in five aromatic classes (floral, fruity, sweet, lactic (cheesy) and other). In addition, statistics (Principal Component Analysis (PCA), Hieratical Clustering Analysis (HCA)) were used aiming to differentiate the analyzed varietal groups. The outcomes have pointed out the existence of distinct clusters connected with ethyl esters or alcohol composition and production year, depending on each examined variety. Full article

(This article belongs to the Topic Advances in Analysis of Food and Beverages)

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12 pages, 1710 KiB

Open AccessEditor’s ChoiceArticle

Pomegranate Juice Clarification Using Ultrafiltration: Influence of the Type of Variety and Degree of Ripeness

by Asunción M. Hidalgo, José A. Macario, Marta Abellán-Baeza, Teresa Sánchez-Moya, Rubén López-Nicolás and Fulgencio Marín-Iniesta

Separations 2024, 11(5), 134; https://doi.org/10.3390/separations11050134 - 26 Apr 2024

Viewed by 1496

Abstract

Fruit consumption guarantees the supply of most of the necessary nutrients for a complete and balanced diet, as it is a relevant source of vitamins, minerals, and antioxidants. In particular, pomegranate has very interesting medicinal properties, such as an anti-inflammatory effect and the [...] Read more.

Fruit consumption guarantees the supply of most of the necessary nutrients for a complete and balanced diet, as it is a relevant source of vitamins, minerals, and antioxidants. In particular, pomegranate has very interesting medicinal properties, such as an anti-inflammatory effect and the protection of the cardiovascular system, among others. During pomegranate juice production, it appears cloudy and must be clarified to remove suspended solids such as colloids and high-molecular weight tannins. The membrane clarification process is a cost-effective alternative to the conventional methods, resulting in a high-quality product. In this work, the clarification of pomegranate juice using the Triple System Model F1 membrane module was carried out for the Mollar and Wonderful varieties with early and late maturity. Three ultrafiltration membranes with different molecular weight cut-off and different chemical compositions were used. The rejection coefficient and permeate flux (which represent the selectivity of the membranes and the process efficiency, respectively) were measured. GR-40PP showed the best results in terms of membrane selectivity and process efficiency, achieving adequate physicochemical juice parameters. Regarding the comparison of the maturity degree, in general terms, the Mollar variety showed better results. Ripe pomegranates showed greater selectivity, while the process efficiency was higher for the early samples. Full article

(This article belongs to the Section Analysis of Natural Products and Pharmaceuticals)

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24 pages, 5748 KiB

Open AccessEditor’s ChoiceReview

Laser Manufacturing of Superwetting Oil–Water Separation Materials: A Review

by Wei Xiong, Linfeng Zhu, Ruisong Jiang and Chaolang Chen

Separations 2024, 11(4), 126; https://doi.org/10.3390/separations11040126 - 19 Apr 2024

Viewed by 1576

Abstract

The frequent occurrence of oil spills and the massive discharge of oily wastewater pose a significant threat to sustainable and healthy human development. Therefore, it is of importance to effectively separate oil–water mixtures. Inspired by nature, many superwetting surfaces/materials for oil–water separation have [...] Read more.

The frequent occurrence of oil spills and the massive discharge of oily wastewater pose a significant threat to sustainable and healthy human development. Therefore, it is of importance to effectively separate oil–water mixtures. Inspired by nature, many superwetting surfaces/materials for oil–water separation have been developed in recent years. However, these surfaces/materials are subject to certain limitations and are unable to fully meet practical needs. With the advancement of laser technology, a novel solution has been provided for fabricating superwetting oil–water separation materials. Based on the design theory and separation mechanism, this paper summarizes the research progress of the laser-fabricated superwetting surfaces/materials for oil–water separation in recent years. First, the basic wetting theory, design strategy, and oil–water separation mechanism of the laser-fabricated materials are introduced in detail. Subsequently, the laser-fabricated oil–water separation materials, including superoleophilic/superhydrophobic materials, superhydrophilic/superoleophobic materials, and materials with reversible or superamphiphilic wettability, are systematically summarized and analyzed. Finally, the challenges and future research directions of laser-fabricated superwetting oil–water separation materials are discussed. Full article

(This article belongs to the Special Issue Advanced Oil–Water Separation Technology)

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19 pages, 4852 KiB

Open AccessEditor’s ChoiceArticle

Adsorption of Fluoride from Water Using Aluminum-Coated Silica Adsorbents: Comparison of Silica Sand and Microcrystalline Silica

by Kiana Modaresahmadi, Amid P. Khodadoust and James Wescott

Separations 2024, 11(4), 125; https://doi.org/10.3390/separations11040125 - 19 Apr 2024

Cited by 1 | Viewed by 1395

Abstract

Two aluminum-coated silica adsorbents were evaluated using silica sand and microcrystalline silica as aluminum-oxide-based adsorbents with different crystalline silica base materials. The aluminum coating contained mainly amorphous aluminum oxides for both aluminum-coated silica adsorbents. The adsorption of fluoride onto both adsorbents was favorable [...] Read more.

Two aluminum-coated silica adsorbents were evaluated using silica sand and microcrystalline silica as aluminum-oxide-based adsorbents with different crystalline silica base materials. The aluminum coating contained mainly amorphous aluminum oxides for both aluminum-coated silica adsorbents. The adsorption of fluoride onto both adsorbents was favorable according to the Langmuir and Freundlich adsorption equations, while the physical adsorption of fluoride occurred for both adsorbents according to the Dubinin–Raduskevish (D-R) equation. The adsorption of fluoride was stronger for aluminum-coated silica sand based on adsorption parameters from the Langmuir, Freundlich, and D-R adsorption equations, with the stronger binding of fluoride likely due to the observed greater specific adsorption. The adsorption capacity determined using the Langmuir equation was about 7 times greater for aluminum-coated microcrystalline silica primarily due to the 1.22-orders-of-magnitude-larger surface area of aluminum-coated microcrystalline silica, whereas the surface-normalized adsorption capacity was 2.4 times greater for aluminum-coated silica sand, possibly due to more aluminum being present on the surface of silica sand. Fluoride adsorption occurred over a broad pH range from 3 to 10 for both adsorbents, with nearly the same pH_PZC of 9.6, while aluminum-coated microcrystalline silica displayed a higher selectivity for fluoride adsorption from different natural water sources. Full article

(This article belongs to the Section Materials in Separation Science)

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15 pages, 2394 KiB

Open AccessEditor’s ChoiceArticle

Selective H₂ Evolution and CO₂ Absorption in Electrolysis of Ethanolamine Aqueous Solutions

by Satoshi Fukada, Ryosuke Sakai, Makoto Oya and Kazunari Katayama

Separations 2023, 10(11), 578; https://doi.org/10.3390/separations10110578 - 20 Nov 2023

Viewed by 1772

Abstract

Selective H₂ evolution and CO₂ absorption in several ethanolamine aqueous solutions are comparatively investigated using a new electrolysis reactor. H₂ bubbles are generated from a cathode in any ethanolamine electrolyte, and its experimental gas evolution rates are correlated by Faraday’s [...] Read more.

Selective H₂ evolution and CO₂ absorption in several ethanolamine aqueous solutions are comparatively investigated using a new electrolysis reactor. H₂ bubbles are generated from a cathode in any ethanolamine electrolyte, and its experimental gas evolution rates are correlated by Faraday’s first rule. No or smaller amounts of CO₂ and N₂ bubbles than stoichiometric ones are generated on an anode through the reaction between hydroxide ions and ethanolamine ones. No CO or O₂ is observed in the system exhaust, and most of the CO₂, along with N_2, is still absorbed in ethanolamine aqueous solutions with the addition of KOH and/or HCOOH under high pH conditions. Variations of the concentrations of coexisting ions dissolved in the electrolytes of mono- or tri-ethanolamine (MEA or TEA) and ethylenediamine (EDA) solutions with CO₂ absorption are calculated using the equilibrium constants to relate the concentrations of solute ions. Electric resistivities of the ethanolamine aqueous solutions are correlated by the pH value and are analyzed in terms of equilibrium constants among the concentrations of coexisting ions. Conditions of the MEA electrolyte to achieve high-performance electrolysis is discussed for selective H₂ generation. Full article

(This article belongs to the Special Issue Advances in CO₂ Adsorptive Separation for CO₂ Capture)

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16 pages, 3907 KiB

Open AccessEditor’s ChoiceArticle

Identifying the Early Post-Mortem VOC Profile from Cadavers in a Morgue Environment Using Comprehensive Two-Dimensional Gas Chromatography

by Darshil Patel, Rushali Dargan, Wesley S. Burr, Benoit Daoust and Shari Forbes

Separations 2023, 10(11), 566; https://doi.org/10.3390/separations10110566 - 10 Nov 2023

Cited by 1 | Viewed by 2779

Abstract

Understanding the VOC profile released during the early post-mortem period is essential for applications in training human remains detection dogs and urban search and rescue operations (USAR) to rapidly locate living and deceased victims. Human cadavers were sampled at the UQTR morgue within [...] Read more.

Understanding the VOC profile released during the early post-mortem period is essential for applications in training human remains detection dogs and urban search and rescue operations (USAR) to rapidly locate living and deceased victims. Human cadavers were sampled at the UQTR morgue within a 0–72 h post-mortem interval. VOC samples were collected from the headspace above the cadavers, using Tenax TA/Carbograph 5TD dual sorbent tubes, and analyzed using GC×GC-TOFMS. Multiple data processing steps, including peak table alignment and filtering, were undertaken using LECO ChromaToF and custom scripts in R programming language. This study identified 104 prevalent VOCs, some of which are linked to human decomposition, while others are connected to the persistence of living scent. Principal Component Analysis (PCA) further highlighted that VOC profiles can change dynamically over time, even in a controlled setting. The findings underscore the complexity and variability in VOC profiles during the early post-mortem period. This variability is influenced by multiple factors including the individual’s biological and physiological conditions. Despite the challenges in characterizing these profiles, the identified VOCs could potentially serve as markers in forensic applications. The study also highlights the need for additional research to build a dataset of VOCs for more robust forensic applications. Full article

(This article belongs to the Special Issue Chemical Separations in Criminalistics)

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25 pages, 4971 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of CO₂ Adsorption Parameters in Fluidised Zeolite 13X Beds Using Non-Linear Multivariate Optimisation

by Alessio Caravella, Giuseppe Prenesti, Salvatore De Luca, Maria Turano, Flaviano Testa and Rossella Girimonte

Separations 2023, 10(11), 558; https://doi.org/10.3390/separations10110558 - 3 Nov 2023

Cited by 1 | Viewed by 3022

Abstract

This work is part of a research project aimed at studying potential sorbents for CO₂ capture. The main parameters characterising the adsorption process of zeolite 13X were derived with the aim of overcoming the limits of experimental analysis and thus predicting the [...] Read more.

This work is part of a research project aimed at studying potential sorbents for CO₂ capture. The main parameters characterising the adsorption process of zeolite 13X were derived with the aim of overcoming the limits of experimental analysis and thus predicting the performances of the materials of interest. In particular, the main parameters that control the adsorption process of CO₂ in zeolite 13X were evaluated through parametric optimisation. This systematic procedure allows for the prediction of the performances of the materials at different operating conditions, identifying the most suitable ones for the case under consideration. Another important application lies in the possibility of a preliminary study of a potential process scale-up for future industrial use. The captured carbon dioxide can be stored or used as a reagent in the production of products with higher economic values, such as methanol, DME and others. Full article

(This article belongs to the Special Issue Advances in CO₂ Adsorptive Separation for CO₂ Capture)

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21 pages, 3743 KiB

Open AccessEditor’s ChoiceArticle

A Rule-Based Automated Chemical Recognition Algorithm for a Multi-Cell Multi-Detector Micro Gas Chromatograph

by Qu Xu, Yutao Qin and Yogesh B. Gianchandani

Separations 2023, 10(11), 555; https://doi.org/10.3390/separations10110555 - 31 Oct 2023

Cited by 1 | Viewed by 1789

Abstract

A chemical recognition algorithm is an integral part of any autonomous microscale gas chromatography (µGC) system for automated chemical analysis. For a multi-detector µGC system, the chemical analysis must account for the retention time of each chemical analyte as well as the relative [...] Read more.

A chemical recognition algorithm is an integral part of any autonomous microscale gas chromatography (µGC) system for automated chemical analysis. For a multi-detector µGC system, the chemical analysis must account for the retention time of each chemical analyte as well as the relative response of each detector to each analyte, i.e., the detector response pattern (DRP). In contrast to the common approaches of heuristically using principal component analysis and machine learning, this paper reports a rule-based automated chemical recognition algorithm for a multi-cell, multi-detector µGC system, in which the DRP is related to theoretical principles; consequently, this algorithm only requires a small amount of calibration data but not extensive training data. For processing both the retention time and the raw DRP, the algorithm applies rules based on expert knowledge to compare the detected peaks; these rules are located in a customized software library. Additionally, the algorithm provides special handling for chromatogram peaks with a small signal-to-noise ratio. It also provides separate special handling for asymmetrical peaks that may result from surface adsorptive analytes. This work also describes an experimental evaluation in which the algorithm used the relative response of two complementary types of capacitive detectors as well as a photoionization detector that were incorporated into the µGC system of interest. In these tests, which were performed on chromatograms with 21–31 peaks for each detector, the true positive rate was 96.3%, the true negative rate was 94.1%, the false positive rate was 5.9%, and the false negative rate was 3.7%. The results demonstrated that the algorithm can support µGC systems for automated chemical screening and early warning applications. Full article

(This article belongs to the Special Issue Development of Materials for Chromatographic Separation)

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15 pages, 2776 KiB

Open AccessEditor’s ChoiceArticle

Application of Choline Chloride-Based Deep Eutectic Solvents in the Synthesis of Hydrazones

by Valentina Bušić, Sunčica Roca and Dajana Gašo-Sokač

Separations 2023, 10(11), 551; https://doi.org/10.3390/separations10110551 - 29 Oct 2023

Cited by 2 | Viewed by 2715

Abstract

The synthesis of 14 hydrazone compounds derived from pyridoxal, pyridine-4-carbaldehyde, and quinoline-2-carbaldehyde using two methods, conventional method in deep eutectic solvents (DESs) and effective combination of ultrasound and DESs, is presented in this paper. In addition, the possibility of using 12 choline chloride [...] Read more.

The synthesis of 14 hydrazone compounds derived from pyridoxal, pyridine-4-carbaldehyde, and quinoline-2-carbaldehyde using two methods, conventional method in deep eutectic solvents (DESs) and effective combination of ultrasound and DESs, is presented in this paper. In addition, the possibility of using 12 choline chloride (ChCl)-based DESs as an alternative to organic solvents was investigated. The results show that the application of ultrasound not only improves the reaction yield but also shortens the reaction time. The prepared compounds synthesized at room temperature were analyzed via NMR spectroscopy and MS spectrometry. The studies confirmed that the DESs ChCl:malonic, oxalic, levulinic, and trans-cinnamic acid can be excellent alternatives to classical organic solvents. By the combined use of DESs and the ultrasonic method, compound 11 was obtained in a nearly quantitative yield of 98% in DES ChCl:oxalic acid. The advantages of using DESs as reaction media are that they are biodegradable, nontoxic, recyclable, and can be easily prepared with inexpensive starting materials. The results of recycling DESs show that they can be used up to the fourth recycling cycle without significantly changing the reaction yield. Full article

(This article belongs to the Special Issue Application of Deep Eutectic Solvents in Green Separation Chemistry)

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22 pages, 856 KiB

Open AccessEditor’s ChoiceArticle

Aroma Profile of Grapevine Chips after Roasting: A Comparative Study of Sorbara and Spergola Cultivars for More Sustainable Oenological Production

by Veronica D’Eusanio, Lorenzo Morelli, Andrea Marchetti and Lorenzo Tassi

Separations 2023, 10(10), 532; https://doi.org/10.3390/separations10100532 - 6 Oct 2023

Cited by 4 | Viewed by 1829

Abstract

This study aimed to compare the aroma profiles of Sorbara and Spergola grapevine prunings roasted at different temperatures (120, 140, 160, 180, 200, and 240 °C). One potential application of grapevine prunings is their use as infusion chips to enhance and improve the [...] Read more.

This study aimed to compare the aroma profiles of Sorbara and Spergola grapevine prunings roasted at different temperatures (120, 140, 160, 180, 200, and 240 °C). One potential application of grapevine prunings is their use as infusion chips to enhance and improve the aging processes of alcoholic beverages and vinegars. Aromatic compounds impart unique flavors and contribute to the complexity of the final products. Thermogravimetry–mass spectrometry coupled with evolved gas analysis (TGA-MS-EGA) was conducted to identify the thermal steps at which substantial changes occurred in the wood matrix. Solid-phase microextraction–gas chromatography–mass spectrometry (SPME-GC-MS) was used for the analysis of volatile compounds. Several key volatile compounds were identified, showing variations in their concentrations as a function of cultivar and roasting temperature. Furan derivatives, such as furfural, and phenolic compounds, such as guaiacol and vanillin, were the two main chemical classes of volatile compounds that predominantly defined the aroma of grapevine chips roasted above 180 °C. At lower roasting temperatures, some aldehydes, such as hexanal and terpenes, defined the aroma profiles of the samples. By repurposing waste materials, this application offers a pathway for environmentally conscious viticulture and sustainable practices within the food industry. Full article

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34 pages, 1646 KiB

Open AccessEditor’s ChoiceReview

Innovative Solutions for Food Analysis: Microextraction Techniques in Lipid Peroxidation Product Detection

by Jorge A. Custodio-Mendoza, Ana M. Ares-Fuentes and Antonia M. Carro

Separations 2023, 10(10), 531; https://doi.org/10.3390/separations10100531 - 4 Oct 2023

Cited by 13 | Viewed by 2753

Abstract

Lipid peroxidation, the most aggressive reaction in food, results in the formation of reactive organic compounds that detrimentally impact food sensory qualities and consumers’ health. While controlled lipid peroxidation can enhance flavors and appearance in certain foods, secondary peroxidation products lead to sensory [...] Read more.

Lipid peroxidation, the most aggressive reaction in food, results in the formation of reactive organic compounds that detrimentally impact food sensory qualities and consumers’ health. While controlled lipid peroxidation can enhance flavors and appearance in certain foods, secondary peroxidation products lead to sensory deterioration in a variety of products, such as oils, alcoholic beverages, and meat. This publication reviews the use of modern analytical techniques for detecting and quantifying carbonyl compounds, i.e., secondary lipid peroxidation products. The paper focuses specifically on microextraction-based methods: dispersive liquid-liquid microextraction (DLLME), solid-phase microextraction (SPME), and gas-diffusion microextraction (GDME). These techniques offer efficient and sensitive approaches to extracting and quantifying lipid oxidation products and contribute to the understanding of oxidative deterioration in various food products. The review outlines recent advancements, challenges, and limitations in these microextraction techniques, as well as emphasizes the potential for further innovation and improvement in the field of food analysis. Full article

(This article belongs to the Special Issue Design and Development of Sample Preparation Procedures for the Determination of Volatile Organic Compounds)

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21 pages, 2144 KiB

Open AccessEditor’s ChoiceArticle

Adsorption of Lactose Using Anion Exchange Resin by Adding Boric Acid from Milk Whey

by Hideo Maruyama and Hideshi Seki

Separations 2023, 10(10), 530; https://doi.org/10.3390/separations10100530 - 3 Oct 2023

Viewed by 2028

Abstract

The influence of adding boric acid (BA) on the adsorption behavior of lactose onto an anion exchange resin (IRA402) was investigated. By adding BA, the amount of lactose adsorbed onto IRA402 was increased ca. 20% compared to without adding BA. In the presence [...] Read more.

The influence of adding boric acid (BA) on the adsorption behavior of lactose onto an anion exchange resin (IRA402) was investigated. By adding BA, the amount of lactose adsorbed onto IRA402 was increased ca. 20% compared to without adding BA. In the presence of BA, ca. 70% of the adsorbed lactose could desorb from IRA402, while the absorbed lactose hardly desorbed in the absence of BA. Lactose molecules were considered to bind to tertiary amine group on IRA402 by Maillard reaction. The optimum conditions of the dosage of BA and pH were found at the molar ratio of BA to lactose ranging from 1–2, and pH 7–9. The kinetics and equilibrium of lactose adsorption could be explained by the Langmuir adsorption model (best model). In the case of a real whey solution, phosphate strongly affected the adsorption behavior and could be removed as precipitation from the whey over pH 10. Whey proteins had little effect on lactose adsorption, which was ca. 30% less than that in the model system. Moreover, the different kinds of whey proteins and amino acids had little effect on the amount adsorbed. Minerals in the whey may also be considered to be responsible for the decreased adsorption in the whey. Full article

(This article belongs to the Section Separation Engineering)

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16 pages, 4470 KiB

Open AccessEditor’s ChoiceArticle

CoFe₂O₄/MoS₂@Au: Multifunction Z-Scheme Heterojunction for SERS Monitoring and Photocatalytic Degradation of Fungicides

by Qirong Dong, Qingyi Wei and Hongbin Pu

Separations 2023, 10(10), 526; https://doi.org/10.3390/separations10100526 - 28 Sep 2023

Cited by 1 | Viewed by 1498

Abstract

Efficient detection and degradation of fungicides are greatly concerned with aquatic food safety. Herein, a multifunction CoFe₂O₄/MoS₂@Au (ACMS) composite was synthesized for crystal violet (CV) and malachite green (MG) photocatalytic degradation and SERS determination. As the construction [...] Read more.

Efficient detection and degradation of fungicides are greatly concerned with aquatic food safety. Herein, a multifunction CoFe₂O₄/MoS₂@Au (ACMS) composite was synthesized for crystal violet (CV) and malachite green (MG) photocatalytic degradation and SERS determination. As the construction of the Z-scheme heterostructure of ACMS, which enhanced the light absorption capability and the separation efficiency of photoexcited carrier significantly, ACMS possessed an excellent photocatalytic performance with a degradation rate of 94.76% for CV under simulated solar light irradiation. Furthermore, the multifunction ACMS exhibited superior SERS capability with a detection limit (LOD) of 4.309 × 10⁻² μg L⁻¹ for MG residues in water. And the ACMS substrates could be utilized to determine the MG residues in crucian carp extract, resulting in a recovery rate of 96.00~116.00%. In addition, such multifunction heterojunctions were performed for in situ monitoring of the photodegradation process. This research opened up a novel perspective on the applications of heterojunction-based multifunction materials for food safety control. Full article

(This article belongs to the Section Environmental Separations)

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20 pages, 5490 KiB

Open AccessEditor’s ChoiceArticle

Development of an Ultrasound-Assisted Emulsification Microextraction Method for the Determination of Volatile Compounds in Wines

by Ioanna Chalvantzi, Aspasia Nisiotou, Georgios Banilas and Athanasios Mallouchos

Separations 2023, 10(10), 525; https://doi.org/10.3390/separations10100525 - 27 Sep 2023

Cited by 2 | Viewed by 1581

Abstract

A fast and simple method based on ultrasound-assisted emulsification microextraction (USAEME) was developed for the analysis of volatile compounds in wines. A full factorial 2⁴ screening design was built to investigate the main factors affecting the extraction of volatile components, namely the [...] Read more.

A fast and simple method based on ultrasound-assisted emulsification microextraction (USAEME) was developed for the analysis of volatile compounds in wines. A full factorial 2⁴ screening design was built to investigate the main factors affecting the extraction of volatile components, namely the volume of extraction solvent, sonication time, salt content, and pH. Then, the factors with significant effects were optimized using an I-optimal design. The optimal value for all the variables studied was reached under the following experimental conditions: volume of extraction solvent 200 μL and salt content 5% m/v. The suitability of the optimized method was evaluated, resulting in very good linearity with coefficients of determination (R²) higher than 0.995 in all cases, while repeatability was lower than 8.4% except for d-limonene and p-cymene. Recoveries higher than 82% were observed for the groups of ethyl esters, acetate esters, alcohols, and terpenoid alcohols (linalool, α-terpineol). The recovery of acids ranged from 70.5% to 88.9%, whereas the three monoterpenes studied (d-limonene, γ-terpinene, p-cymene) were not extracted satisfactorily. The proposed method was effectively applied for the analysis of volatile compounds in laboratory-scale fermentations with selected strains of Saccharomyces cerevisiae. Full article

(This article belongs to the Special Issue Design and Development of Sample Preparation Procedures for the Determination of Volatile Organic Compounds)

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27 pages, 465 KiB

Open AccessEditor’s ChoiceReview

Organic Solvent Nanofiltration and Data-Driven Approaches

by Pieter-Jan Piccard, Pedro Borges, Bart Cleuren, Jef Hooyberghs and Anita Buekenhoudt

Separations 2023, 10(9), 516; https://doi.org/10.3390/separations10090516 - 19 Sep 2023

Cited by 1 | Viewed by 2006

Abstract

Organic solvent nanofiltration (OSN) is a membrane separation method that has gained much interest due to its promising ability to offer an energy-lean alternative for traditional thermal separation methods. Industrial acceptance, however, is held back by the slow process of membrane screening based [...] Read more.

Organic solvent nanofiltration (OSN) is a membrane separation method that has gained much interest due to its promising ability to offer an energy-lean alternative for traditional thermal separation methods. Industrial acceptance, however, is held back by the slow process of membrane screening based on trial and error for each solute-solvent couple to be separated. Such time-consuming screening is necessary due to the absence of predictive models, caused by a lack of fundamental understanding of the complex separation mechanism complicated by the wide variety of solute and solvent properties, and the importance of all mutual solute-solvent-membrane affinities and competing interactions. Recently, data-driven approaches have gained a lot of attention due to their unprecedented predictive power, significantly outperforming traditional mechanistic models. In this review, we give an overview of both mechanistic models and the recent advances in data-driven modeling. In addition to other reviews, we want to emphasize the coherence of all mechanistic models and discuss their relevance in an increasingly data-driven field. We reflect on the use of data in the field of OSN and its compliance with the FAIR principles, and we give an overview of the state of the art of data-driven models in OSN. The review can serve as inspiration for any further modeling activities, both mechanistic and data-driven, in the field. Full article

(This article belongs to the Collection State of the Art in Separation Science)

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19 pages, 17398 KiB

Open AccessEditor’s ChoiceArticle

Extraction of Gallium from the Brown Corundum Dust with a One-Step Alkaline Leaching Process

by Juhua Zhang, Cong Gao, Xujie Hui and Yuwei Chang

Separations 2023, 10(9), 510; https://doi.org/10.3390/separations10090510 - 15 Sep 2023

Cited by 1 | Viewed by 2054

Abstract

Brown corundum dust, which is created during the manufacturing of brown corundum using bauxite as the raw material, is a vital carrier of gallium. To ascertain the presence of the contained gallium, the brown corundum dust was measured and characterized (XRF, XRD, ICP-OES, [...] Read more.

Brown corundum dust, which is created during the manufacturing of brown corundum using bauxite as the raw material, is a vital carrier of gallium. To ascertain the presence of the contained gallium, the brown corundum dust was measured and characterized (XRF, XRD, ICP-OES, EPMA, SEM-EDS, etc.). Gallium was extracted from the brown corundum dust using a one-step alkali leaching process, and thermodynamic calculations were utilized to assess the viability of the leaching reactions. The effects of leaching parameters (NaOH solution concentration, leaching time, leaching temperature, solid–liquid ratio and stirring speed) on the recovery of gallium during the leaching process were investigated. A gallium recovery of 96.83% was discovered to be possible with the following parameters: 200 g/L of NaOH, 363 K for the leaching temperature, 60 min for the leaching time, 1:10 g/mL for the solid–liquid ratio, and 850 rpm for the stirring rate. Gallium extraction was negatively impacted by raising the leaching temperature above 363 K and the concentration of NaOH solution above 200 g/L due to the accelerated side reactions between Na⁺, K⁺, SiO₄⁴⁻ and AlO₂⁻, which led to the precipitation of aluminosilicates that absorbed gallium from the solution. The influences of leaching parameters such as the temperature, NaOH solution concentration, and solid–liquid ratio on the leaching kinetics were examined. It was demonstrated that the leaching process followed the unreacted shrinking core model, that the interfacial diffusion associated with the contacting surface area served as the controlling step, and that the apparent activation energy was 42.83 kJ/mol. It turned out that the final kinetic equation was 1/(1 − α)^1/3 − 1 = 4.34 × 10⁴ × (C_NaOH)^2.12 (L/S)^0.43exp[−42835/(RT)] t. Full article

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16 pages, 6007 KiB

Open AccessEditor’s ChoiceArticle

Enhanced CO₂ Capture by Sorption on Electrospun Poly (Methyl Methacrylate)

by Michele Ciulla, Valentino Canale, Rafal D. Wolicki, Serena Pilato, Pantaleone Bruni, Stefania Ferrari, Gabriella Siani, Antonella Fontana and Pietro Di Profio

Separations 2023, 10(9), 505; https://doi.org/10.3390/separations10090505 - 14 Sep 2023

Cited by 5 | Viewed by 1535

Abstract

Poly(methyl methacrylate) (PMMA) is characterized by high CO₂ capture yield under mild pressures and temperatures. A morphological modification of powdery amorphous PMMA (pPMMA) is carried out by electrospinning to increase the surface/volume ratio of the resulting electrospun PMMAs (ePMMAs). This modification improves [...] Read more.

Poly(methyl methacrylate) (PMMA) is characterized by high CO₂ capture yield under mild pressures and temperatures. A morphological modification of powdery amorphous PMMA (pPMMA) is carried out by electrospinning to increase the surface/volume ratio of the resulting electrospun PMMAs (ePMMAs). This modification improves the kinetics and the capture yields. The rate constants observed for ePMMAs are two to three times higher than those for pPMMA, reaching 90% saturation values within 5–7 s. The amount of sorbed CO₂ is up to eleven times higher for ePMMAs at 1 °C, and the highest difference in captured CO₂ amount is observed at the lowest tested pressure of 1 MPa. The operating life of the ePMMAs shows a 5% yield loss after ten consecutive runs, indicating good durability. Spent electrospun PMMAs after several cycles of CO₂ sorption-desorption can be regenerated by melting and again electrospinning the molten mass, resulting in a CO₂ capture performance that is undistinguishable from that observed with fresh ePMMA. Scanning electron and atomic force microscopies show a reduction in surface roughness after gas exposure, possibly due to the plasticization effect of CO₂. This study shows the potential of electrospun PMMAs as solid sorbents for carbon capture from natural gas or pre-combustion and oxyfuel combustion processes. Full article

(This article belongs to the Special Issue Green Solvents and Advanced Materials for Gas Capture and Separation)

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17 pages, 2125 KiB

Open AccessEditor’s ChoiceArticle

Comprehensive Profiling of Terpenes and Terpenoids in Different Cannabis Strains Using GC × GC-TOFMS

by Jasmeen Kaur, Ning Sun and Jane E. Hill

Separations 2023, 10(9), 500; https://doi.org/10.3390/separations10090500 - 13 Sep 2023

Cited by 2 | Viewed by 4803

Abstract

Cannabis contains a wide range of terpenes and terpenoids that are mainly responsible for their distinctive aroma and flavor. These compounds have also demonstrated therapeutic effects either alone and/or as synergistic compounds with other terpenes, terpenoids, and/or cannabinoids. Several studies have attempted to [...] Read more.

Cannabis contains a wide range of terpenes and terpenoids that are mainly responsible for their distinctive aroma and flavor. These compounds have also demonstrated therapeutic effects either alone and/or as synergistic compounds with other terpenes, terpenoids, and/or cannabinoids. Several studies have attempted to fully characterize terpenes and terpenoids in cannabis; however, most of these studies used one-dimensional gas chromatography, which often results in the co-elution of the compounds. In the present study, we analyzed terpenes and terpenoids in the dried flowers of six cannabis strains using a two-dimensional gas chromatograph time-of-flight mass spectrometer (GC × GC-TOFMS). A total of 146 terpenes and terpenoids were detected across all six cannabis strains with an enhanced separation of 16 terpenes and terpenoids in the second dimension. Additionally, we achieved enhanced separation of four terpenes and terpenoids from a standard mixture in the second dimension. Chemical differences were observed in the number and relative abundance of monoterpenes, monoterpenoids, sesquiterpenes, and sesquiterpenoids in all six strains. We were also able to identify four new terpenoids in cannabis, which are reported here for the first time. Full article

(This article belongs to the Special Issue Comprehensive Separations of Complex Mixtures by Gas Chromatography/Mass Spectrometry)

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37 pages, 2331 KiB

Open AccessEditor’s ChoiceArticle

An In-Depth Stability Study of the Essential Oils from Mentha × piperita, Mentha spicata, Origanum vulgare, and Thymus vulgaris: The Impact of Thermal and Storage Conditions

by Eugenia Ganosi, Christina Barda, Maria-Eleni Grafakou, Michael Ch. Rallis and Helen Skaltsa

Separations 2023, 10(9), 488; https://doi.org/10.3390/separations10090488 - 7 Sep 2023

Viewed by 2125

Abstract

In recent years, there has been a growing scientific interest in essential oils due to their therapeutic and aromatic properties and as potential alternative natural additives for use as preservatives or antibiotics. However, the literature lacks a comprehensive understanding of their stability and [...] Read more.

In recent years, there has been a growing scientific interest in essential oils due to their therapeutic and aromatic properties and as potential alternative natural additives for use as preservatives or antibiotics. However, the literature lacks a comprehensive understanding of their stability and how their composition and properties change over time under various conditions. Through this paper, we aim to enhance the existing literature by providing deeper insights into the stability of essential oils and the sustainability of chemical composition in a time-based approach under various conditions. Therefore, four essential oils of the Lamiaceae family (Origanum vulgare, Thymus vulgaris, Mentha spicata, and M. x piperita) were evaluated with respect to their chemical variation influenced by several factors, such as thermal and storage conditions. Three types of containers were utilized to store the essential oils, i.e., glass ampoules, glass tubes, and metallic containers with plastic caps, for up to six months in −20 °C, 4 °C, 23 °C (with or without light exposure), 35 °C, and 45 °C. Samples were routinely analyzed by GC-MS and components were subjected to principal component analysis to ascertain whether the identified constituents may be useful in reflecting the stability of the analyzed samples. The main compounds appeared to be more stable, while the degradation of minor constituents (<1.0%) occurred in all four essential oils despite the storage conditions. Overall, apart from a slight variation in the chemical load, essential oils can be considered stable for various applications, especially those stored under low oxygen availability conditions. Full article

(This article belongs to the Special Issue Biological and Toxicological Activities of Plant Extracts and Their Extraction Methods)

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24 pages, 697 KiB

Open AccessEditor’s ChoiceReview

Carnosic Acid and Carnosol: Analytical Methods for Their Determination in Plants, Foods and Biological Samples

by Christiana Mantzourani, Petros A. Tarantilis and Maroula G. Kokotou

Separations 2023, 10(9), 481; https://doi.org/10.3390/separations10090481 - 2 Sep 2023

Cited by 2 | Viewed by 4694

Abstract

Among the various phytochemicals, which are present in Lamiaceae plants, carnosic acid and carnosol stand out. Carnosic acid is a phenolic diterpene carrying two phenolic hydroxyl groups and a carboxyl group, while carnosol carries a lactone moiety in addition to phenolic hydroxyls. Both [...] Read more.

Among the various phytochemicals, which are present in Lamiaceae plants, carnosic acid and carnosol stand out. Carnosic acid is a phenolic diterpene carrying two phenolic hydroxyl groups and a carboxyl group, while carnosol carries a lactone moiety in addition to phenolic hydroxyls. Both these phenolic diterpenes exhibit interesting biological properties, such as antioxidant, anticancer, anti-inflammatory and neuroprotective activities. In this review, we summarize the existing analytical methods for the determination of carnosic acid and carnosol, primarily in plants, but also in foods and biological samples. Due to the biological importance of carnosic acid and carnosol, a variety of analytical methods, including high-performance liquid chromatography–ultra violet (HPLC–UV), liquid chromatography–mass spectrometry (LC–MS) and capillary electrophoresis (CE), were developed for their determination. In addition, we discuss the extraction methods applied for their isolation from plants and in brief the bioactivities of these phytochemicals. Full article

(This article belongs to the Special Issue Application of Chromatography in Pharmaceutical and Biomedical Analysis)

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22 pages, 7059 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Fluoride Removal from Water Sources by Adsorption on MOFs

by Athanasia K. Tolkou and Anastasios I. Zouboulis

Separations 2023, 10(9), 467; https://doi.org/10.3390/separations10090467 - 24 Aug 2023

Cited by 10 | Viewed by 2832

Abstract

Fluoride is present in several groundwaters due to natural or anthropogenic origins. Although it is necessary for physiological human functions (in small amounts, i.e., 0.5–1.2 mg/L), it could be very harmful when it exceeds the maximum permissible concentration limit of 1.5 mg/L (according [...] Read more.

Fluoride is present in several groundwaters due to natural or anthropogenic origins. Although it is necessary for physiological human functions (in small amounts, i.e., 0.5–1.2 mg/L), it could be very harmful when it exceeds the maximum permissible concentration limit of 1.5 mg/L (according to WHO). Among the numerous technologies for removing fluoride from waters, metal–organic framework (MOF) materials are considered to be promising adsorbents due to their advantages of high porosity, high specific surface area, diverse functions and easy modification. In this study, the synthesis of MOFs and the progress of their application to the removal of fluoride from contaminated water, as published in the recent literature mainly over the past five years, are reviewed. The adsorption mechanism(s) and its main characteristics, such as effect of initial fluoride concentration, adsorbent dosage, solution pH, contact time, adsorption capacity, thermodynamic and regeneration studies, etc., for the removal of fluoride with the addition of different MOFs are compared. According to these comparisons, the hydrothermal/solvothermal synthesis method is most commonly used for the preparation of MOFs, whereas higher BET surface areas are shown by specific MOFs based on aluminum metal ions. The main fluoride adsorption mechanisms were found to be electrostatic attraction and/or complexation. The most common pH for conducting experiments was 7.0, but several examined materials were found to be effective over a wide pH range. Four to six regeneration cycles were successfully applied on average, regarding the MOFs under review, whereas in the majority of these cases, the sorption process was found to be endothermic. Full article

(This article belongs to the Special Issue Development of Mesoporous Materials for Adsorption and Recovery of Metals)

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22 pages, 1095 KiB

Open AccessEditor’s ChoiceReview

Adsorption-Based Pretreatment of Irrigation Water to Prevent Water Quality Issues

by Tamás Kucserka, Gábor István Németh, Ivett Pálfi, Zsolt L. Kiss, Etelka Tombácz and Ildikó Galambos

Separations 2023, 10(9), 468; https://doi.org/10.3390/separations10090468 - 24 Aug 2023

Cited by 3 | Viewed by 1824

Abstract

Access to and the use of irrigation water of adequate quality and targeted nutrient supplementation have become more widespread in recent years. Both crop quality and the irrigation system lifetime are affected by the quality of the water used for irrigation. Micro-irrigation (e.g., [...] Read more.

Access to and the use of irrigation water of adequate quality and targeted nutrient supplementation have become more widespread in recent years. Both crop quality and the irrigation system lifetime are affected by the quality of the water used for irrigation. Micro-irrigation (e.g., drip and sprinkle) is becoming increasingly common alongside the more typical irrigation methods, but it requires expertise and pre-treatment to ensure a proper water supply. The most significant problem is clogging, which can greatly reduce irrigation efficiency. Treatment for irrigation purposes mainly depends on the contaminants that are present in the water. The main treatment options available are biological, electromagnetic and electrostatic treatments, but these have a wide range of effectiveness levels compared to membrane separation technologies. In addition, adsorption treatments are also available, which, depending on the adsorbent used, can greatly improve the pre-treatment of irrigation water. This work provides an overview of adsorbents suitable for the treatment of irrigation water and their effectiveness. The separation of interfering components via adsorption is effective and promising for future application as the expected irrigation demands increase. Full article

(This article belongs to the Topic Sustainable Water Purification Technologies for Multiple Applications)

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19 pages, 5711 KiB

Open AccessEditor’s ChoiceArticle

Carob Pulp Flour Extract Obtained by a Microwave-Assisted Extraction Technique: A Prospective Antioxidant and Antimicrobial Agent

by Jana Zahorec, Dragana Šoronja-Simović, Sunčica Kocić-Tanackov, Sandra Bulut, Nikola Martić, Katarina Bijelić, Danica Božović and Branimir Pavlić

Separations 2023, 10(9), 465; https://doi.org/10.3390/separations10090465 - 24 Aug 2023

Cited by 1 | Viewed by 1593

Abstract

In this study, carob pulp flour (CF) extract was characterized as a high-value antioxidant and antimicrobial agent. CF extracts were obtained using microwave-assisted extraction (MAE) and optimization of the MAE process was accomplished using response surface methodology. The studied processing parameters of MAE [...] Read more.

In this study, carob pulp flour (CF) extract was characterized as a high-value antioxidant and antimicrobial agent. CF extracts were obtained using microwave-assisted extraction (MAE) and optimization of the MAE process was accomplished using response surface methodology. The studied processing parameters of MAE were the liquid/solid (L/S) ratio (10–30 mL/g), extraction time (15–35 min), and ethanol concentration (40–80% w/w). The efficiency of the extraction of valuable compounds from CF was evaluated by the determining extraction yield (Y), total phenolic(TP), total flavonoid (TF) content, and antioxidant activity (DPPH, FRAP, and ABTS). The optimized MAE parameters for maximizing the yields of target compounds and antioxidant activity were the L/S ratio 30 mL/g, extraction time 35 min, and ethanol concentration 40%. The experimentally obtained values for TP, TF, DPPH, FRAP, and ABTS were 1609.92 GAE/100 g, 271.92 CE/100 g, 99.02 µMTE/g, 50.45 µM Fe²⁺/g, and 110.55 µMTE/g, respectively. The optimized CF extract was compared with the CF extracts obtained by conventional solid–liquid extraction (S/L) and ultrasound-assisted extraction (UAE) and was found to be more beneficial due to a 30% higher yield of TP and TF and 30–80% higher antioxidant activity. The phenolic profiles of the three extracts were quite similar. The microdilution method confirmed the antibacterial activity of MAE and S/L extracts while the antifungal effect was not observed. Full article

(This article belongs to the Special Issue Novel Applications of Separation Technology)

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19 pages, 3311 KiB

Open AccessEditor’s ChoiceArticle

Potential Use of Agricultural Waste—Carob Kibbles (Ceratonia siliqua L.) as a Biosorbent for Removing Boron from Wastewater

by Luz Adriana Díaz, Jorge Dias Carlier, Izabela Michalak and María Clara Costa

Separations 2023, 10(9), 464; https://doi.org/10.3390/separations10090464 - 24 Aug 2023

Viewed by 1548

Abstract

The release of boron (B) into the environment as a result of anthropogenic activity modifies sustainable natural conditions, thus affecting ecosystems. To meet water quality regulations, commercial and natural boron adsorbents are available to reduce its concentrations in industrial effluents, with the former [...] Read more.

The release of boron (B) into the environment as a result of anthropogenic activity modifies sustainable natural conditions, thus affecting ecosystems. To meet water quality regulations, commercial and natural boron adsorbents are available to reduce its concentrations in industrial effluents, with the former being not only more expensive but also less sustainable. In the publication, the biosorption parameters of carob kibbles (Ceratonia siliqua L.) were optimized in order to remove boron from aqueous solutions using batch experiments. The biosorbent used in the present research was agro-waste biomass provided by the local locust-beam gum industry. Boron removal by carob kibbles was favored at high initial pH values, and this capacity was found to be a function of boron initial concentration, biosorbent content in the solution, and particle size. The change in temperature did not affect the potential of biomass to remove boron. The highest boron removal efficiency (55.1%) was achieved under the following optimal conditions: 50 g/L biosorbent dose (Cs), with particle size range 0.025–0.106 mm, for the initial concentration (C₀) of boron in the solution of 100 mg/L, at an initial pH of 11.5, for 5 h at 25 °C. This investigation suggests that carob kibble agro-waste can be valorized as a biosorbent to remove boron from wastewater, and the boron-loaded residue may eventually be explored as a new boron-fertilizer. Full article

(This article belongs to the Special Issue (Bio)-Sorbents for Water Treatment and Soil Remediation)

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17 pages, 800 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Solid–Liquid Extraction of Bioactive Molecules from White Grape Skin: Optimization and Near-Infrared Spectroscopy

by Tea Sokač Cvetnić, Korina Krog, Maja Benković, Tamara Jurina, Davor Valinger, Jasenka Gajdoš Kljusurić, Ivana Radojčić Redovniković and Ana Jurinjak Tušek

Separations 2023, 10(8), 452; https://doi.org/10.3390/separations10080452 - 14 Aug 2023

Cited by 2 | Viewed by 1487

Abstract

In this work, the solid–liquid extraction of bioactive molecules from grape skin was performed using water as the extraction solvent. The effects of extraction time (t = 60, 75, and 90 min), extraction temperature (T = 40, 60, and 80 °C), [...] Read more.

In this work, the solid–liquid extraction of bioactive molecules from grape skin was performed using water as the extraction solvent. The effects of extraction time (t = 60, 75, and 90 min), extraction temperature (T = 40, 60, and 80 °C), solid–liquid phase ratio (S/L = 10, 20, and 30 g/L), and mixing speed (rpm = 250, 500, and 750 1/min) on the total dissolved solids, extraction yield, concentration of total polyphenols, and antioxidant activity were determined using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) methods. According to response surface modeling, the optimal extraction conditions were t = 75 min, T = 80 °C, S/L = 30 g/L, and rpm = 750 1/min, and under optimal process conditions, 8.38 mg_GAE/g_d.m. was obtained. Furthermore, the potential of near-infrared (NIR) spectroscopy coupled with artificial neural network (ANN) modeling for prediction of the physical and chemical properties of prepared extracts was also analyzed. The use of ANN modeling demonstrated highly favorable correlations between the NIR spectra and all the variables tested, particularly the total dissolved solids (TDS) and antioxidant activity measured using the FRAP method. As a result, ANN modeling proved to be a valuable tool for predicting the concentration of total polyphenols, the antioxidant activity, and the extraction yield of a plant extract based on its NIR spectra. Full article

(This article belongs to the Section Bioanalysis/Clinical Analysis)

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18 pages, 1141 KiB

Open AccessEditor’s ChoiceArticle

The Development and Validation of a Targeted LC-HRAM-MS/MS Methodology to Separate and Quantify p-Synephrine and m-Synephrine in Dietary Supplements and Herbal Preparations

by Celine Vanhee, Sophia Barhdadi, Angélique Kamugisha, Tanika Van Mulders, Kevin Vanbrusselen, Marie Willocx and Eric Deconinck

Separations 2023, 10(8), 444; https://doi.org/10.3390/separations10080444 - 9 Aug 2023

Cited by 2 | Viewed by 1598

Abstract

Dietary supplements containing Citrus aurantium or p-synephrine remain very popular in Europe and the United States of America (USA). They are primarily sold as weight loss enhancers, although their efficacy and the safety are still under scrutiny. To this end, several countries [...] Read more.

Dietary supplements containing Citrus aurantium or p-synephrine remain very popular in Europe and the United States of America (USA). They are primarily sold as weight loss enhancers, although their efficacy and the safety are still under scrutiny. To this end, several countries have set maximum threshold levels of p-synephrine that are permitted in dietary supplements. Moreover, there have also been reports of possible chemical adulteration of these supplements with the synthetic positional isomer, m-synephrine, known to be used as a medicinal product. Therefore, it is pivotal for regulatory agencies to be able to discriminate between the two positional isomers and also quantify the amount of each when encountered in dietary supplements. Here, we present the development and the validation of a simple and fast “dilute and shoot” procedure, employing liquid chromatographic (LC) separation in combination with high-resolution accurate mass (HRAM) tandem mass spectroscopy (LC-HRAM-MS/MS) to separate these two isomers and subsequently quantify them. The quantification methodology has been validated using the “total error approach”, applying accuracy profiles, and is consequently compliant with ISO17025. Moreover, ten real-life samples, either purchased online or encountered by Belgian regulatory agencies, were analyzed using the described procedure. Startlingly, only one sample out of ten was compliant with Belgian legislation in terms of labeling, the presence of a batch number, expiration date and dosage (with a tolerated error of ±20%). Moreover, three samples also contained banned substances such as yohimbine and sibutramine. Full article

(This article belongs to the Special Issue Recent Advances and Trends in Dietary Supplement Analysis)

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24 pages, 4875 KiB

Open AccessEditor’s ChoiceArticle

Biosynthesis of Salbutamol-4′-O-sulfate as Reference for Identification of Intake Routes and Enantiopure Salbutamol Administration by Achiral UHPLC-MS/MS

by Annika Lisa Jendretzki, Lukas Corbinian Harps, Yanan Sun, Felix Bredendiek, Matthias Bureik, Ulrich Girreser, Xavier de la Torre, Francesco M. Botrè and Maria Kristina Parr

Separations 2023, 10(8), 427; https://doi.org/10.3390/separations10080427 - 28 Jul 2023

Cited by 1 | Viewed by 2323

Abstract

The aim of the study was a comprehensive and quantitative determination of salbutamol and its sulfoconjugated major metabolite in urine samples using achiral ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Therefore, salbutamol-4′-O-sulfate was biosynthesized as a reference using genetically modified fission [...] Read more.

The aim of the study was a comprehensive and quantitative determination of salbutamol and its sulfoconjugated major metabolite in urine samples using achiral ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Therefore, salbutamol-4′-O-sulfate was biosynthesized as a reference using genetically modified fission yeast cells, and the product was subsequently characterized by NMR and HRMS. In competitive sports, salbutamol is classified as a prohibited drug; however, inhalation at therapeutic doses is permitted with a maximum allowance of 600 µg/8 h. In contrast, the enantiopure levosalbutamol is prohibited under any condition. For analytical discrimination, the amount of salbutamol and its main metabolite excreted in the urine was studied. As proof of concept, a longitudinal study in one healthy volunteer was performed in order to investigate excreted amounts and to study potential discrimination using achiral chromatography. Discrimination of administration of racemic salbutamol or the enantiopure levosalbutamol was not achieved by solely analyzing salbutamol as the parent compound. However, a distinction was possible by evaluation of the proportion of salbutamol-4′-O-sulfate in relation to salbutamol. Therefore, reference material of metabolites is of great importance in doping control, especially for threshold substances. Full article

(This article belongs to the Special Issue Application of Hyphenated Techniques in Bioanalysis and Metabolite Identification)

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19 pages, 1119 KiB

Open AccessEditor’s ChoiceArticle

Phytochemical Profile, Antioxidant Activity and Cholinesterase Inhibition Potential of Essential Oil and Extracts of Teucrium montanum from Bosnia and Herzegovina

by Mejra Bektasevic, Mladenka Jurin, Marin Roje and Olivera Politeo

Separations 2023, 10(8), 421; https://doi.org/10.3390/separations10080421 - 26 Jul 2023

Cited by 9 | Viewed by 2384

Abstract

Bioactive compounds from plants play an important role in slowing many neurodegenerative diseases, such as Alzheimer’s disease, by inhibiting cholinesterase enzymes. Studies have shown that oxidative stress is associated with the development of Alzheimer’s disease. In traditional medicine of Bosnia and Herzegovina, Teucrium [...] Read more.

Bioactive compounds from plants play an important role in slowing many neurodegenerative diseases, such as Alzheimer’s disease, by inhibiting cholinesterase enzymes. Studies have shown that oxidative stress is associated with the development of Alzheimer’s disease. In traditional medicine of Bosnia and Herzegovina, Teucrium montanum is used to treat numerous diseases. The chemical composition and biological activity of the essential oil (EO) and aqueous (AE) and methanol extract (ME) of this plant were studied. The chemical composition of EO was studied using GC-MS, while the composition of the extracts was studied using HPLC-DAD. Antioxidant activity was tested using the DPPH and FRAP methods. The protection of lipids and proteins from oxidation was tested using the ammonium thiocyanate and BSA oxidation methods. The ability to inhibit cholinesterases was tested by the Ellman method. The main identified EO compounds were α-cadinol, ß-selinene, δ-cadinene, epi-α-cadinol, germacrene D-4-ol, and α-pinene. The main phenolic compounds of the extracts were p-coumaric acid, ellagic acid and caffeic acid. The tested extracts showed good antioxidant radical scavenging and reducing potential and a very good ability to protect lipids and proteins from oxidation. The EO showed moderate AChE and BChE inhibition potential, while the extracts showed weak or no ability. Full article

(This article belongs to the Special Issue Separation, Analysis and Biological Evaluation of Bioactive Compounds)

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18 pages, 3155 KiB

Open AccessEditor’s ChoiceReview

Advances in Cork Use in Adsorption Applications: An Overview of the Last Decade of Research

by João Jesus, Raquel Nunes da Silva and Ariana Pintor

Separations 2023, 10(7), 390; https://doi.org/10.3390/separations10070390 - 3 Jul 2023

Cited by 5 | Viewed by 2633

Abstract

Cork-based adsorbents have been gathering interest from the research community since the 1990s. A first review was published on this topic in 2012. Still, in the last decade, novel activated carbons and biochars, in multiple applications, have been produced using cork as a [...] Read more.

Cork-based adsorbents have been gathering interest from the research community since the 1990s. A first review was published on this topic in 2012. Still, in the last decade, novel activated carbons and biochars, in multiple applications, have been produced using cork as a raw material. This review presents these novel insights into the properties of cork, in its various forms, and how they relate to adsorption capacity. Details on new preparation methodologies and respective characteristics of cork-based activated carbons and biochars are thoroughly compared, and patterns are identified. Finally, the adsorption capacity of these materials in experimental conditions is reviewed for different compounds: heavy metals, organics, and gaseous pollutants. This review provides a complete picture of the kind and quality of different cork forms, their relative economic value, and how their conversion into activated carbons and biochars can contribute to a more circular economy by producing adsorbents that aid in the reduction of multiple pollution types. Full article

(This article belongs to the Special Issue Removal of Metals or Other Toxic Substances from Wastewaters by Natural Sorbents)

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23 pages, 2691 KiB

Open AccessEditor’s ChoiceArticle

Quantitation of Formoterol, Salbutamol, and Salbutamol-4′-O-Sulfate in Human Urine and Serum via UHPLC-MS/MS

by Lukas C. Harps, Daniel A. Bizjak, Ulrich Girreser, Martina Zügel, Jürgen M. Steinacker, Patrick Diel and Maria Kristina Parr

Separations 2023, 10(7), 368; https://doi.org/10.3390/separations10070368 - 22 Jun 2023

Cited by 4 | Viewed by 1652

Abstract

The adrenergic beta-2 agonists formoterol and salbutamol are used for the treatment of asthma and COPD but are also misused in sports competitions. Therefore, they are included in WADA regulations. Both drugs are mainly excreted in urine after administration via inhalation. A four-armed, [...] Read more.

The adrenergic beta-2 agonists formoterol and salbutamol are used for the treatment of asthma and COPD but are also misused in sports competitions. Therefore, they are included in WADA regulations. Both drugs are mainly excreted in urine after administration via inhalation. A four-armed, double-blind cross-over clinical trial was conducted involving endurance-trained participants (12 females and 12 males). Inhalation dosages of 36 μg formoterol, 1200 μg salbutamol, a combination of both, or a placebo were administered before exercise. Serum and urine were collected after exercise and 3 and 24 h after administration. Here, we show the successful quantitation of formoterol, salbutamol, and its phase II metabolite salbutamol-4′-O-sulfate in all urine and serum samples using ultra-high performance liquid chromatography–tandem mass spectrometry. In the serum analysis, results of up to 14.2 pg/mL formoterol, 10.0 ng/mL salbutamol, and 21.4 ng/mL salbutamol-4′-O-sulfate (calculated as salbutamol equivalent) were found. In urine, maximum concentrations (after deglucuronidation) were 17.2 ng/mL formoterol, 948.5 ng/mL salbutamol, and 2738.5 ng/mL salbutamol-4′-O-sulfate. Sex-specific differences in serum concentrations as well as in urinary excretion were observed. The results pronounce the importance of the implementation and elucidation of phase II metabolites to quantitation methods in antidoping. Full article

(This article belongs to the Special Issue Application of Hyphenated Techniques in Bioanalysis and Metabolite Identification)

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17 pages, 1837 KiB

Open AccessEditor’s ChoiceArticle

Comprehensive Metabolite Fingerprinting of Australian Black and Green Olives and Their Antioxidant and Pharmacokinetics Properties

by Akhtar Ali, Farhad Ahmadi, Jeremy J. Cottrell and Frank R. Dunshea

Separations 2023, 10(6), 354; https://doi.org/10.3390/separations10060354 - 13 Jun 2023

Cited by 6 | Viewed by 2514

Abstract

Polyphenols, especially flavonoids, are well-known for their bioactive antioxidant properties. Therefore, this study aimed to analyze Australian black (ripe) and green olives (unripe) for phenolic and non-phenolic metabolites, antioxidant activities, and pharmacokinetic properties. Liquid chromatography–mass spectrometry coupled with quadrupole–time of flight (LC–ESI–QTOF–MS/MS) was [...] Read more.

Polyphenols, especially flavonoids, are well-known for their bioactive antioxidant properties. Therefore, this study aimed to analyze Australian black (ripe) and green olives (unripe) for phenolic and non-phenolic metabolites, antioxidant activities, and pharmacokinetic properties. Liquid chromatography–mass spectrometry coupled with quadrupole–time of flight (LC–ESI–QTOF–MS/MS) was applied to elucidate the composition, identification, and characterization of bioactive metabolites from Australian olives. This study identified 110 metabolites, including phenolic acids, flavonoids, stilbenes, lignans, and other compounds (phenolic terpenes, tyrosols, fatty acids, and terpenoids). Luteolin (flavonoid) and verbascoside (hydroxycinnamic acid) are identified with higher concentrations in black olives. Black (ripe) olives were measured at a higher TPC (10.94 ± 0.42 mg GAE/g) and total antioxidant potential than green olives. The pharmacokinetic properties (absorption, distribution, metabolism, excretion, toxicity) of phenolic compounds for human health were evaluated to predict the potential of the most abundant metabolites in olives. Gastrointestinal absorption and Caco-2 cell permeability of metabolites in olives were also predicted. This study will develop into further research to identify the Australian olives’ therapeutic, nutraceutical, and phytopharmaceutical potential. Full article

(This article belongs to the Special Issue Isolation, Elucidation and Synthesis of Bioactive Natural Products)

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17 pages, 1070 KiB

Open AccessEditor’s ChoiceArticle

Particle Cut Diameter Prediction of Uniflow Cyclone Systems with Fuzzy System Analysis

by Vinzenz Klapper, Giovanni Luzi, Benedict Prah and Antonio Delgado

Separations 2023, 10(6), 345; https://doi.org/10.3390/separations10060345 - 5 Jun 2023

Cited by 1 | Viewed by 2719

Abstract

Cyclones are devices used in various industries to remove particulate matter from gases and liquids. Commonly used in the power generation, cement, and mining industries, cyclones improve the efficiency and longevity of equipment by removing dust and other small particles that can cause [...] Read more.

Cyclones are devices used in various industries to remove particulate matter from gases and liquids. Commonly used in the power generation, cement, and mining industries, cyclones improve the efficiency and longevity of equipment by removing dust and other small particles that can cause wear and damage. Among centrifugal separation, reverse-flow cyclones are primarily used for particle separation, which can reach heights of several meters on an industrial scale and therefore, are difficult to access for maintenance. A uniflow centrifugal segregation system avoids these drawbacks of reverse-flow cyclones since their accessibility is good and their height usually does not exceed their diameter. The efficiency is a critical aspect of separating systems. This study systematically examines the collection efficiency for particles ranging from 1

μ m

to 29

μ m

in diameter based on varying vane angles of the swirl inducer at flow rates ranging from 130

L

s^{- 1}

to 236

L

s^{- 1}

. Full article

(This article belongs to the Collection Feature Paper Collection in Section 'Purification Technology')

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19 pages, 8233 KiB

Open AccessEditor’s ChoiceArticle

Particulate Matter Detachment from a Magnetizable Single Fiber Applying Magnetic Forces in Ambient Air

by Julia Szabadi, Jörg Meyer and Achim Dittler

Separations 2023, 10(5), 297; https://doi.org/10.3390/separations10050297 - 7 May 2023

Cited by 2 | Viewed by 1620

Abstract

The potential utilization of magnetic effects in gas particle separation is a current subject of research. This paper demonstrates for the first time that a single magnetizable filter fiber can be deflected by a magnetically induced excitation for a selected combination of parameters, [...] Read more.

The potential utilization of magnetic effects in gas particle separation is a current subject of research. This paper demonstrates for the first time that a single magnetizable filter fiber can be deflected by a magnetically induced excitation for a selected combination of parameters, resulting in the removal of deposited particle structures with high detachment levels. A correlation between the magnetic flux density and achieved acceleration to overcome the adhesive forces/strength of the particle structure was determined. The degree of detachment after each regeneration was calculated by comparing the projection area before and after detachment using high-speed images. At a magnetic flux density of B = 38.5 mT, accelerations of maximum a = 105 m·s⁻² are achieved, depending on the axial position along the single fiber. The degrees of regeneration achieved at these parameters depend on the amount of fiber loading and on the fiber orientation in the gravitational field. The horizontal orientation of the fiber leads to an increased reattachment of precedingly detached particle structures after deflection compared to a vertical orientation. High particle loading on the fiber results in enhanced detachment by inertia. Under the most favorable process conditions investigated, detachment levels of >90% are achieved. Full article

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23 pages, 3386 KiB

Open AccessEditor’s ChoiceArticle

Comparative Study of Conventional, Microwave-Assisted and Supercritical Fluid Extraction of Bioactive Compounds from Microalgae: The Case of Scenedesmus obliquus

by Ioulia Georgiopoulou, Vasiliki Louli and Kostis Magoulas

Separations 2023, 10(5), 290; https://doi.org/10.3390/separations10050290 - 4 May 2023

Cited by 6 | Viewed by 2669

Abstract

The recovery of bioactive products with green processes is a critical topic for the research and industry fields. In this work, the application of solid–liquid (SLE), microwave-assisted extraction (MAE) with aq. ethanol 90% v/v and supercritical fluid extraction (SFE) with CO [...] Read more.

The recovery of bioactive products with green processes is a critical topic for the research and industry fields. In this work, the application of solid–liquid (SLE), microwave-assisted extraction (MAE) with aq. ethanol 90% v/v and supercritical fluid extraction (SFE) with CO₂ for the recovery of biocomponents from Scenedesmus obliquus is studied. The effects examined were temperature (30–60 °C), time (6–24 h), and solvent-to-biomass ratio (20–90 mL_solv/g_biom) for SLE, temperature (40–60 °C), time (5–25 min), solvent-to-biomass ratio (20–90 mL_solv/g_biom), and microwave power (300–800 W) for MAE, and temperature (40–60 °C), pressure (110–250 bar), solvent flow rate (20–40 g_solv/min), and cosolvent presence (0, 10% w/w ethanol) for SFE in relation to the extract’s yield, phenolic, chlorophyll, carotenoid content, and antioxidant activity. The optimum extraction conditions determined were 30 °C, 24 h, and 90 mL_solv/g_biom for SLE, 60 °C, 5 min, 90 mL_solv/g_biom, and 300 W for MAE, and 60 °C, 250 bar, and 40 g_solv/min for SFE. Additionally, a kinetic SFE study was conducted and the obtained results were satisfactorily correlated using Sovová’s model. The comparison between the methods proved MAE’s efficiency in all terms compared to SLE. Moreover, SFE was accompanied with the lowest yield and chlorophyll content, yet led to an increased carotenoid content and improved antioxidant activity. Finally, the cosolvent addition significantly improved SFE’s yield and led to the most superior extract. Full article

(This article belongs to the Special Issue Separation, Extraction and Purification of Natural Products)

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19 pages, 4166 KiB

Open AccessEditor’s ChoiceArticle

Improvement of Gd(III) Solvent Extraction by 4-Benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one: Non-Aqueous Systems

by Maria Atanassova and Rositsa Kukeva

Separations 2023, 10(5), 286; https://doi.org/10.3390/separations10050286 - 3 May 2023

Cited by 3 | Viewed by 2095

Abstract

The study of the liquid–liquid extraction of gadolinium (Gd(III) ion) with a chelating compound, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), and the determination of the process parameters are presented by employing two ionic liquids, namely, ([C₁C_nim⁺][Tf₂N⁻], n [...] Read more.

The study of the liquid–liquid extraction of gadolinium (Gd(III) ion) with a chelating compound, 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP), and the determination of the process parameters are presented by employing two ionic liquids, namely, ([C₁C_nim⁺][Tf₂N⁻], n = 4, 10) and CHCl_3, as diluents. Compared to CHCl₃, the ionic liquid offers increased distribution ratios in an aqueous medium. A step forward, enhanced solvent extraction, and improved separation upon the addition of ethylene glycol are demonstrated, i.e., a boost of two immiscible organic phases, compared to traditional aqueous solutions. However, this is noticeable when using CHCl₃, but unfortunately not with ionic liquid combination, [C₁C₁₀im⁺][Tf₂N⁻]. Several conclusions are given, highlighting the role of the ionic diluent in complexation processes and selectivity with an employment of the chelating agent HP for various metal s-, p-, d-, and f-cations, i.e., nearly 25 metals. A detailed evaluation of the selectivity between these metals was made when changing both the aqueous phase completely with ethylene glycol or partially with glycerol (1:1). Electron paramagnetic resonance (EPR) spectroscopy has been used to study the established chemical species in the obtained organic extracts, such as Gd³⁺, Fe³⁺, Cu²⁺, and Cr³⁺, with unpaired electrons. Full article

(This article belongs to the Topic Green Twist in Solvent Extraction and Separation of Metal Species)

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18 pages, 2583 KiB

Open AccessEditor’s ChoiceArticle

Method Development and Validation for the Simultaneous Quantitation of Pentoxifylline, Its Pharmacologically Active Metabolites, and Donepezil Using LC-MS/MS in Rat Plasma: Its Application to a Pharmacokinetic Study

by Sanghee Choi, Wang-Seob Shim, Jiyoung Yoon, Doowon Choi, Eunseo Song, Yeo Jin Choi, Soo-Heui Paik and Kyung-Tae Lee

Separations 2023, 10(5), 276; https://doi.org/10.3390/separations10050276 - 24 Apr 2023

Cited by 3 | Viewed by 1950

Abstract

This study developed a simple, rapid, reproducible, and analytical method using liquid chromatography and electrospray ionization (ESI) with tandem mass spectrometry (LC-MS/MS) to simultaneously quantify pentoxifylline (PTX), its pharmacological active metabolites, lisofylline (PTX-M1) and 1-(3-carboxypropyl)-3,7-dimethylxanthine (PTX-M5), and donepezil (DNP) in rat plasma, using [...] Read more.

This study developed a simple, rapid, reproducible, and analytical method using liquid chromatography and electrospray ionization (ESI) with tandem mass spectrometry (LC-MS/MS) to simultaneously quantify pentoxifylline (PTX), its pharmacological active metabolites, lisofylline (PTX-M1) and 1-(3-carboxypropyl)-3,7-dimethylxanthine (PTX-M5), and donepezil (DNP) in rat plasma, using PTX-d6 and DNP-d7 as the internal standards. The LC-MS/MS procedure was performed at the ESI interface, operating in positive ionization and multiple reaction monitoring (MRM) modes; the monitoring of transitions comprised m/z 279.3 > 181.1 for PTX, m/z 281.1 > 263.1 > 160.90 for PTX-M1, m/z 267.1 > 249.0 > 220.9 for PTX-M5, m/z 380.3 > 90.9 for DNP, m/z 285.3 > 187.1 for PTX-d6 (IS1), and m/z 387.3 > 98.3 for DNP-d7 (IS2). After plasma protein precipitation (PP) with methanol, chromatographic separation was performed with an Imtakt Cadenza^® CD-C18 (100 × 3 mm, 3 µm) column, using an isocratic mobile phase consisting of 0.1% formic acid in water and methanol (20:80, v/v) at a flow rate of 0.2 mL/min. The retention times of DNP, PTX-M5, PTX, and PTX-M1 were 2.24, 2.50, 2.68, and 2.72 min, respectively, with a total run time of 5 min. This method was validated over a linear concentration range of 5–8000, 10–5000, 20–15,000, and 2–500 ng mL⁻¹ for PTX, PTX-M1, PTX-M5, and DNP, respectively, with a high correlation coefficient (r² ≥ 0.99). The established method was fully validated in terms of selectivity, the lower limit of quantitation, precision, accuracy, recovery, matrix effect, stability, and dilution integrity according to the regulatory guidelines from the U.S. Food and Drug Administration and the Korea Ministry of Food and Drug Safety. The validated method was successfully applied to a pharmacokinetic study on the concurrent administration of DNP and PTX in rats. Full article

(This article belongs to the Section Bioanalysis/Clinical Analysis)

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15 pages, 934 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Cucumis metuliferus L. Fruits Extract with Antioxidant, Anti-Inflammatory, and Antidiabetic Properties as Source of Ursolic Acid

by Anna Cazanevscaia Busuioc, Giorgiana Valentina Costea, Andreea Veronica Dediu Botezatu, Bianca Furdui and Rodica Mihaela Dinica

Separations 2023, 10(5), 274; https://doi.org/10.3390/separations10050274 - 23 Apr 2023

Cited by 6 | Viewed by 2390

Abstract

To identify healthy, nutritious, and sustainable plant-based products rich in biologically active compounds, this present study was conducted, and the phytochemical composition and biological properties of the hydroethanolic ultrasound-assisted extract of the fruits of Cucumis metuliferus were investigated. Cucumis metuliferus is an unexplored [...] Read more.

To identify healthy, nutritious, and sustainable plant-based products rich in biologically active compounds, this present study was conducted, and the phytochemical composition and biological properties of the hydroethanolic ultrasound-assisted extract of the fruits of Cucumis metuliferus were investigated. Cucumis metuliferus is an unexplored fruit of a climbing plant in the Cucurbitaceae family, widely distributed in the tropical and subtropical regions of sub-Saharan Africa and whose nutritional and medicinal benefits are well known in African countries, especially. Therefore, its cultivation in other regions could influence chemical composition. The structural identification of the compounds from the hydroethanolic extract from Cucumis metuliferus fruits grown in Romania was carried out by chromatographic techniques (HPLC). The main compounds identified were catechin, oleanolic acid, ursolic acid, p-coumaric acid, and epicatechin. Subsequently, a method was proposed to isolate and characterize ursolic acid, one of the major compounds. The obtained results show that the hydroethanolic extract is rich in antioxidant compounds evaluated using the DPPH radical inhibition method (IC₅₀ = 32.74 ± 0.02 µg/mL) and ABTS cation radical inhibition method (IC₅₀ = 11.37 ± 0.07 µg/mL). It also demonstrate in vitro anti-inflammatory activities, such as anti-lipoxygenase (IC₅₀ = 32.90 ± 0.05 µg/mL) and anti-proteinase (IC₅₀ = 16.34 ± 0.07 µg/mL), and antidiabetic properties by inhibiting α-amylase (IC₅₀ = 429.541 ± 0.25 µg/mL) and β-glucosidase activity (IC₅₀ = 385.685 ± 0.76 µg/mL). Therefore, C. metuliferus fruits could be effectively used in the development of various health-promoting products, being not only appetizing, with spectacular appearance and with extended storage life, but also curative and healthy. Full article

(This article belongs to the Special Issue Separation, Extraction and Purification of Natural Products)

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30 pages, 3393 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Mass Transfer and Droplet Behaviors in Liquid-Liquid Extraction Process Based on Multi-Scale Perspective: A Review

by Sicen Yu, Jiyizhe Zhang, Shaowei Li, Zhuo Chen and Yundong Wang

Separations 2023, 10(4), 264; https://doi.org/10.3390/separations10040264 - 18 Apr 2023

Cited by 5 | Viewed by 7460

Abstract

Liquid-liquid extraction is an important separation technology in the chemical industry, and its separation efficiency depends on thermodynamics (two-phase equilibrium), hydrodynamics (two-phase mixing and contact), and mass transfer (molecular diffusion). For hydrodynamics, the dispersion size of droplets reflects the mixing of two phases [...] Read more.

Liquid-liquid extraction is an important separation technology in the chemical industry, and its separation efficiency depends on thermodynamics (two-phase equilibrium), hydrodynamics (two-phase mixing and contact), and mass transfer (molecular diffusion). For hydrodynamics, the dispersion size of droplets reflects the mixing of two phases and determines the mass transfer contact area of the two phases. Therefore, a deep understanding of the droplet dispersion mechanism can help guide process intensification. The mass transfer and droplet behaviors in the liquid-liquid extraction process are reviewed based on three scales: equipment, droplets, and the interface between two liquids. Studies on the interaction between mass transfer and other performance parameters in extraction equipment as well as liquid-liquid two-phase flow models are reviewed at the equipment scale. The behaviors of droplet breakage and coalescence and the kernel function of the population balance equation are reviewed at the droplet scale. Studies on dynamic interfacial tension and interaction between interfaces are reviewed at the interface scale. Finally, the connection among each scale is summarized, the existing problems are analyzed, and some future research directions are proposed in the last section. Full article

(This article belongs to the Special Issue Advances in Separation Engineering)

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