Separations

11 pages, 1371 KiB

Open AccessEditor’s ChoiceArticle

LC-MS Phytochemical Screening, In Vitro Antioxidant, Antimicrobial and Anticancer Activity of Microalgae Nannochloropsis oculata Extract

by Adil Farooq Wali, Yusra Al Dhaheri, Jayachithra Ramakrishna Pillai, Ahlam Mushtaq, Padma G. M. Rao, Syed Arman Rabbani, Aimen Firdous, Mohamed Soliman Elshikh and Dunia A. Al Farraj

Separations 2020, 7(4), 54; https://doi.org/10.3390/separations7040054 - 8 Oct 2020

Cited by 33 | Viewed by 6041

Abstract

Nowadays, marine microalgae are recognized to be a considerably novel and rich origin of bioactive moieties utilized in the sectors of nutraceuticals and pharmaceuticals. In the present study, Nannochloropsis oculata extract (AME) was associated with a wide variety of pharmacological studies such as [...] Read more.

Nowadays, marine microalgae are recognized to be a considerably novel and rich origin of bioactive moieties utilized in the sectors of nutraceuticals and pharmaceuticals. In the present study, Nannochloropsis oculata extract (AME) was associated with a wide variety of pharmacological studies such as in vitro antioxidant, antibacterial, and antifungal and anticancer activity (MDA-MB-231) in cancer cells through in vitro models. In the study, the chemical composition and structure of the bioactive compounds found in the AME extract were studied using the LC-MS technique. The results of the anticancer activity showed a decrease in the percentage of cell viability of the MDA-MB-231 cells in a concentration- and time-dependent manner (400 μg/mL at 24 h, 300 μg/mL at 48 h, and 200 μg/mL at 72 h). We have also observed morphological changes in the cells that could be associated with treatment with AME extract. Our observation of the AME extract-treated MDA-MB231 cells under light microscopy showed that when the concentration increased, the number of cells began to decrease. As far as LC-MS analysis is concerned, it showed the presence of the bioactive molecules was terpenoids along with carotenoids, polyphenolic and fatty acids. The result revealed that the AME extract exhibited noteworthy in vitro free radical scavenging potential, with an IC₅₀ value of 52.10 ± 0.85 µg/L in DPPH assay, 122.84 ± 2.32 µg/mL in H₂O₂ assay and, 96.95 ± 1.68 µg/mL in ABTS assay. The activity was found to be highly significant against bacteria (Gram-positive and negative) and moderately significant against fungal strain with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)/minimum fungicidal concentration (MFC) values between 15.63 and 500 µg/mL. Full article

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32 pages, 2703 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Role of Ionic Liquids in Composites in Analytical Sample Preparation

by Adrián Gutiérrez-Serpa, Patricia I. Napolitano-Tabares, Jakub Šulc, Idaira Pacheco-Fernández and Verónica Pino

Separations 2020, 7(3), 37; https://doi.org/10.3390/separations7030037 - 6 Jul 2020

Cited by 23 | Viewed by 6173

Abstract

Ionic liquids (ILs) are a group of non-conventional salts with melting points below 100 °C. Apart from their negligible vapor pressure at room temperature, high thermal stability, and impressive solvation properties, ILs are characterized by their tunability. Given such nearly infinite combinations of [...] Read more.

Ionic liquids (ILs) are a group of non-conventional salts with melting points below 100 °C. Apart from their negligible vapor pressure at room temperature, high thermal stability, and impressive solvation properties, ILs are characterized by their tunability. Given such nearly infinite combinations of cations and anions, and the easy modification of their structures, ILs with specific properties can be synthesized. These characteristics have attracted attention regarding their use as extraction phases in analytical sample preparation methods, particularly in liquid-phase extraction methods. Given the liquid nature of most common ILs, their incorporation in analytical sample preparation methods using solid sorbents requires the preparation of solid derivatives, such as polymeric ILs, or the combination of ILs with other materials to prepare solid IL-based composites. In this sense, many solid composites based on ILs have been prepared with improved features, including magnetic particles, carbonaceous materials, polymers, silica materials, and metal-organic frameworks, as additional materials forming the composites. This review aims to give an overview on the preparation and applications of IL-based composites in analytical sample preparation in the period 2017–2020, paying attention to the role of the IL material in those composites to understand the effect of the individual components in the sorbent. Full article

(This article belongs to the Special Issue Recent Advances on Ionic Liquid Uses in Separation Techniques)

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14 pages, 896 KiB

Open AccessEditor’s ChoiceArticle

Pigments Content (Chlorophylls, Fucoxanthin and Phycobiliproteins) of Different Commercial Dried Algae

by Catarina Osório, Susana Machado, Juliana Peixoto, Sílvia Bessada, Filipa B. Pimentel, Rita C. Alves and M. Beatriz P. P. Oliveira

Separations 2020, 7(2), 33; https://doi.org/10.3390/separations7020033 - 11 Jun 2020

Cited by 108 | Viewed by 14044

Abstract

Algae are a complex, polyphyletic group of organisms, affordable and naturally rich in nutrients, but also valuable sources of structurally diverse bioactive substances such as natural pigments. The aim of this work was to evaluate the polar and non-polar pigment contents of different [...] Read more.

Algae are a complex, polyphyletic group of organisms, affordable and naturally rich in nutrients, but also valuable sources of structurally diverse bioactive substances such as natural pigments. The aim of this work was to evaluate the polar and non-polar pigment contents of different commercial dried algae (brown: Himanthalia elongata, Undaria pinnatifida, Laminaria ochroleuca; red: Porphyra spp.; and a blue-green microalga: Spirulina spp.). The pigment extraction was carried out using different solvents (100% methanol, 100% methanol acid free, 100% ethanol, 90% acetone, N,N-dimethylformamide, dimethyl sulfoxide-water (4:1, v/v) and pH 6.8 phosphate buffer), selected according to their affinity for each class of pigments. Acetone proved to be an efficient solvent to extract chlorophylls from brown and red algae, but not from Spirulina spp. Porphyra spp. presented considerably higher levels of all pigments compared to brown algae, although Spirulina spp. presented significantly higher (p < 0.05) levels of chlorophylls, carotenoids and phycobiliproteins, compared to all macroalgae. The content of fucoxanthin extracted from the three brown algae was highly correlated to the carotenoid content. Within this group, Himanthalia elongata presented the highest fucoxanthin/total carotenoids ratio. Although the yield of extraction depended on the solvent used, the algae studied herein are an interesting source of pigments of great value for a wide range of applications. Full article

(This article belongs to the Special Issue Extraction and Isolation of Natural Products)

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20 pages, 3856 KiB

Open AccessEditor’s ChoiceReview

Hunting Molecules in Complex Matrices with SPME Arrows: A Review

by Jason S. Herrington, German A. Gómez-Ríos, Colton Myers, Gary Stidsen and David S. Bell

Separations 2020, 7(1), 12; https://doi.org/10.3390/separations7010012 - 15 Feb 2020

Cited by 63 | Viewed by 8605

Abstract

Thirty years since the invention and public disclosure of solid phase microextraction (SPME), the technology continues evolving and inspiring several other green extraction technologies amenable for the collection of small molecules present in complex matrices. In this manuscript, we review the fundamental and [...] Read more.

Thirty years since the invention and public disclosure of solid phase microextraction (SPME), the technology continues evolving and inspiring several other green extraction technologies amenable for the collection of small molecules present in complex matrices. In this manuscript, we review the fundamental and operational aspects of a novel SPME geometry that can be used to “hunt” target molecules in complex matrices: the SPME Arrow. In addition, a series of applications in environmental, food, cannabis and forensic analysis are succinctly covered. Finally, special emphasis is placed on novel interfaces to analytical instrumentation, as well as recent developments in coating materials for the SPME Arrow. Full article

(This article belongs to the Special Issue Development of Alternative Green Sample Preparation Techniques)

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27 pages, 1471 KiB

Open AccessEditor’s ChoiceReview

Evolution of Environmentally Friendly Strategies for Metal Extraction

by Govind Sharma Shyam Sunder, Sandhya Adhikari, Ahmad Rohanifar, Abiral Poudel and Jon R. Kirchhoff

Separations 2020, 7(1), 4; https://doi.org/10.3390/separations7010004 - 6 Jan 2020

Cited by 49 | Viewed by 10839

Abstract

The demand for the recovery of valuable metals and the need to understand the impact of heavy metals in the environment on human and aquatic life has led to the development of new methods for the extraction, recovery, and analysis of metal ions. [...] Read more.

The demand for the recovery of valuable metals and the need to understand the impact of heavy metals in the environment on human and aquatic life has led to the development of new methods for the extraction, recovery, and analysis of metal ions. With special emphasis on environmentally friendly approaches, efforts have been made to consider strategies that minimize the use of organic solvents, apply micromethodology, limit waste, reduce costs, are safe, and utilize benign or reusable materials. This review discusses recent developments in liquid- and solid-phase extraction techniques. Liquid-based methods include advances in the application of aqueous two- and three-phase systems, liquid membranes, and cloud point extraction. Recent progress in exploiting new sorbent materials for solid-phase extraction (SPE), solid-phase microextraction (SPME), and bulk extractions will also be discussed. Full article

(This article belongs to the Special Issue Development of Alternative Green Sample Preparation Techniques)

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22 pages, 1517 KiB

Open AccessEditor’s ChoiceReview

Returning to Nature for the Design of Sorptive Phases in Solid-Phase Microextraction

by Gabriela Mafra, María Teresa García-Valverde, Jaime Millán-Santiago, Eduardo Carasek, Rafael Lucena and Soledad Cárdenas

Separations 2020, 7(1), 2; https://doi.org/10.3390/separations7010002 - 29 Dec 2019

Cited by 54 | Viewed by 5875

Abstract

Green analytical chemistry principles aim to minimize the negative impact of analytical procedures in the environment, which can be considered both at close (to ensure the safety of the analysts) and global (to conserve our natural resources) levels. These principles suggest, among other [...] Read more.

Green analytical chemistry principles aim to minimize the negative impact of analytical procedures in the environment, which can be considered both at close (to ensure the safety of the analysts) and global (to conserve our natural resources) levels. These principles suggest, among other guidelines, the reduction/minimization of the sample treatment and the use of renewable sources when possible. The first aspect is largely fulfilled by microextraction, which is considered to be among the greenest sample treatment techniques. The second consideration is attainable if natural products are used as raw materials for the preparation of new extraction phases. This strategy is in line with the change in our production system, which is being gradually moved from a linear model (take–make–dispose) to a circular one (including reusing and recycling as key terms). This article reviews the potential of natural products as sorbents in extraction and microextraction techniques from the synergic perspectives of two research groups working on the topic. The article covers the use of unmodified natural materials and the modified ones (although the latter has a less green character) to draw a general picture of the usefulness of the materials. Full article

(This article belongs to the Special Issue Advances in Solid-Phase Microextraction)

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29 pages, 3934 KiB

Open AccessEditor’s ChoiceReview

Metal–Organic Frameworks as Key Materials for Solid-Phase Microextraction Devices—A Review

by Adrián Gutiérrez-Serpa, Idaira Pacheco-Fernández, Jorge Pasán and Verónica Pino

Separations 2019, 6(4), 47; https://doi.org/10.3390/separations6040047 - 2 Oct 2019

Cited by 89 | Viewed by 11933

Abstract

Metal–organic frameworks (MOFs) have attracted recently considerable attention in analytical sample preparation, particularly when used as novel sorbent materials in solid-phase microextraction (SPME). MOFs are highly ordered porous crystalline structures, full of cavities. They are formed by inorganic centers (metal ion atoms or [...] Read more.

Metal–organic frameworks (MOFs) have attracted recently considerable attention in analytical sample preparation, particularly when used as novel sorbent materials in solid-phase microextraction (SPME). MOFs are highly ordered porous crystalline structures, full of cavities. They are formed by inorganic centers (metal ion atoms or metal clusters) and organic linkers connected by covalent coordination bonds. Depending on the ratio of such precursors and the synthetic conditions, the characteristics of the resulting MOF vary significantly, thus drifting into a countless number of interesting materials with unique properties. Among astonishing features of MOFs, their high chemical and thermal stability, easy tuneability, simple synthesis, and impressive surface area (which is the highest known), are the most attractive characteristics that makes them outstanding materials in SPME. This review offers an overview on the current state of the use of MOFs in different SPME configurations, in all cases covering extraction devices coated with (or incorporating) MOFs, with particular emphases in their preparation. Full article

(This article belongs to the Special Issue Advances in Solid-Phase Microextraction)

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21 pages, 3923 KiB

Open AccessEditor’s ChoiceReview

Metal-Organic Frameworks in Green Analytical Chemistry

by Priscilla Rocío-Bautista, Iván Taima-Mancera, Jorge Pasán and Verónica Pino

Separations 2019, 6(3), 33; https://doi.org/10.3390/separations6030033 - 27 Jun 2019

Cited by 95 | Viewed by 12366

Abstract

Metal-organic frameworks (MOFs) are porous hybrid materials composed of metal ions and organic linkers, characterized by their crystallinity and by the highest known surface areas. MOFs structures present accessible cages, tunnels and modifiable pores, together with adequate mechanical and thermal stability. Their outstanding [...] Read more.

Metal-organic frameworks (MOFs) are porous hybrid materials composed of metal ions and organic linkers, characterized by their crystallinity and by the highest known surface areas. MOFs structures present accessible cages, tunnels and modifiable pores, together with adequate mechanical and thermal stability. Their outstanding properties have led to their recognition as revolutionary materials in recent years. Analytical chemistry has also benefited from the potential of MOF applications. MOFs succeed as sorbent materials in extraction and microextraction procedures, as sensors, and as stationary or pseudo-stationary phases in chromatographic systems. To date, around 100 different MOFs form part of those analytical applications. This review intends to give an overview on the use of MOFs in analytical chemistry in recent years (2017–2019) within the framework of green analytical chemistry requirements, with a particular emphasis on possible toxicity issues of neat MOFs and trends to ensure green approaches in their preparation. Full article

(This article belongs to the Special Issue Development of Alternative Green Sample Preparation Techniques)

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47 pages, 6339 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Chromatographic Techniques in the Research Area of Lithium Ion Batteries: Current State-of-the-Art

by Yannick Philipp Stenzel, Fabian Horsthemke, Martin Winter and Sascha Nowak

Separations 2019, 6(2), 26; https://doi.org/10.3390/separations6020026 - 13 May 2019

Cited by 46 | Viewed by 12524

Abstract

Lithium ion batteries (LIBs) are widely used in numerous application areas, including portable consumer electronics, medicine, grid storage, electric vehicles and hybrid electric vehicles. One major challenge during operation and storage is the degradation of the cell constituents, which is called aging. This [...] Read more.

Lithium ion batteries (LIBs) are widely used in numerous application areas, including portable consumer electronics, medicine, grid storage, electric vehicles and hybrid electric vehicles. One major challenge during operation and storage is the degradation of the cell constituents, which is called aging. This phenomenon drastically reduces both storage lifetime and cycle lifetime. Due to numerous aging effects, originating from both the individual LIB cell constituents as well as their interactions, a wide variety of instruments and methods are necessary for aging investigations. In particular, chromatographic methods are frequently applied for the analysis of the typically used liquid non-aqueous battery electrolytes based on organic solvents or ionic liquids. Moreover, chromatographic methods have also been recently used to investigate the composition of electrode materials. In this review, we will give an overview of the current state of chromatographic methods in the context of LIB cell research. Full article

(This article belongs to the Special Issue Analytic Techniques for Lithium Ion Batteries Analysis)

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22 pages, 1052 KiB

Open AccessEditor’s ChoiceReview

Total and Free Fatty Acids Analysis in Milk and Dairy Fat

by Gustavo Amores and Mailo Virto

Separations 2019, 6(1), 14; https://doi.org/10.3390/separations6010014 - 5 Mar 2019

Cited by 74 | Viewed by 24917

Abstract

Dairy fat is one of the most complex natural fats because of its fatty acid (FA) composition. Ruminant dairy fat contains more than 400 different FA varying in carbon chain length, and degree, position and configuration of unsaturation. The following article reviews the [...] Read more.

Dairy fat is one of the most complex natural fats because of its fatty acid (FA) composition. Ruminant dairy fat contains more than 400 different FA varying in carbon chain length, and degree, position and configuration of unsaturation. The following article reviews the different methods available to analyze FA (both total and free) in milk and dairy products. The most widely used methodology for separating and analyzing dairy FA is gas chromatography, coupled to a flame ionization detector (CG-FID). Alternatively, gas chromatography coupled to a mass spectrometer (GC-MS) is also used. After lipid extraction, total FA (TFA) are commonly converted into their methyl esters (fatty acid methyl esters, FAME) prior to chromatographic analysis. In contrast, free FA (FFA) can be analyzed after conversion to FAME or directly as FFA after extraction from the product. One of the key questions when analyzing FAME from TFA is the selection of a proper column for separating them, which depends mainly on the objective of the analysis. Quantification is best achieved by the internal standard method. Recently, near-infrared spectroscopy (NIRS), Raman spectroscopy (RS) and nuclear magnetic resonance (NMR) have been reported as promising techniques to analyze FA in milk and dairy products. Full article

(This article belongs to the Special Issue Separation Techniques for Dairy Analysis)

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15 pages, 967 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Hydrophobic Deep Eutectic Solvents for Extraction

by Amos K. Dwamena

Separations 2019, 6(1), 9; https://doi.org/10.3390/separations6010009 - 12 Feb 2019

Cited by 181 | Viewed by 21708

Abstract

In the over 1,800 articles published since their inception in 2001, most deep eutectic solvents (DES) synthesized have been hydrophilic. The low cost, low toxicity, and bioavailability of DES make the solvent ‘green’ and sustainable for diverse applications. Conversely, the hydrophilicity of DES [...] Read more.

In the over 1,800 articles published since their inception in 2001, most deep eutectic solvents (DES) synthesized have been hydrophilic. The low cost, low toxicity, and bioavailability of DES make the solvent ‘green’ and sustainable for diverse applications. Conversely, the hydrophilicity of DES limits their practical application to only polar compounds, which is a major drawback of the solvent. For the past three years, hydrophobic deep eutectic solvents (HDES) have emerged as an alternative extractive media capable of extracting non-polar organic and inorganic molecules from aqueous environments. Due to the infancy of HDES, for the first time, this mini-review summarizes the recent developmental advances in HDES synthesis, applications, challenges, and future perspectives of the solvent. In the future, it is believed HDES will replace the majority of toxic organic solvents used for analytical purposes. Full article

(This article belongs to the Special Issue Recent Advances on Ionic Liquid Uses in Separation Techniques)

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