Analytica, Volume 5, Issue 4 (December 2024) – 12 articles

Substituted phenols, including chlorophenols, are important analytes, particularly in the context of environmental analysis. Chlorophenols are formed during the disinfection of drinking water by chlorination and are important water pollutants. Gas chromatography–mass spectrometry (GC-MS) is an important method for the analysis of chlorophenols. Retention indices are used in GC-MS analysis to improve the accuracy of identification. Our research reveals that the retention indices currently available for substituted phenols are erroneous in a number of cases. We report reliable retention index values for pentafluorophenol, 5-methoxy-2-nitrophenol, 4-cyanophenol (stationary phase: 5%-phenyl-polymethylsiloxane), 3-methoxyphenol, 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,3-dichlorophenol, 2,5-dichlorophenol, 2,6-dichlorophenol, 3,4-dichlorophenol, 3,5-dichlorophenol, 2,3,5-trichlorophenol, 2,3,6-trichlorophenol, 2,4,5-trichlorophenol, and 2,4,6-trichlorophenol (stationary phase: polyethylene glycol modified with 2-nitroterephthalic acid). The structures of the standard samples were confirmed, and measurements were performed under various conditions. The analysis of the causes of the incorrect records appearing in the well-known NIST database was also carried out. Full article

Saquinavir is a drug used as an HIV treatment, with recent reports of new uses. It has poor aqueous solubility and very low oral bioavailability. However, when prepared in a eutectic mixture with the natural bioenhancer, piperine, it demonstrated improvements in these drawbacks. Therefore, considering that EMs can be easily produced and scaled-up, it could potentially be used in new pharmaceutical formulations. For this purpose, an analytical method capable of quantifying SQV in the presence of PIP is required for quality control purposes. In this context, UV–Vis equipment is simpler to use and cheaper than HPLC, and it is commonly available in most laboratories. Therefore, a derivative spectrophotometry method at 245 nm was developed and validated to quantify SQV. The method showed good linearity from 0.5 to 100.0 mg/L, with a limit of detection and limit of quantification of 0.331 mg/L and 0.468 mg/L, respectively. Furthermore, it was precise, accurate, and demonstrated good specificity up to a 1:4.3 SQV:PIP ratio. Consequently, the results demonstrate that the method can be employed for SQV quantification in the presence of PIP as an economical and simple technique. This contribution could be the basis for a quality control technique for these types of products. Full article

We report a workflow and a software description for digital image colorimetry aimed at obtaining a quantitative dose–response curve and the minimal inhibitory concentration in the Resazurin Microtiter Assay (REMA) test of the activity of antimycobacterial drugs. The principle of this analysis is based on the newly established correspondence between the intensity of the ${\mathrm{a}}^{*}$ channel of the CIE L*a*b* colour space and the concentration of resorufin produced in the course of this test. The whole procedure can be carried out using free software. It has sufficiently mild requirements for the quality of colour images, which can be taken by a typical smartphone camera. Thus, the approach does not impose additional costs on the medical examination points and is widely accessible. Its efficiency is verified by applying it to the case of two representatives of substituted 2-(quinolin-4-yl) imidazolines. The direct comparison with the data on the indicator’s fluorescence obtained using a commercial microplate reader argues that the proposed approach provides results of the same range of accuracy on the quantitative level. As a result, it would be possible to apply the strategy not only for new low-cost studies but also for expanding databases on drug candidates by quantitatively reprocessing existing data, which were earlier documented by images of microplates but analysed only qualitatively. Full article

Boron nitride nanostructures (BNNs), including nanotubes, nanosheets, and nanoribbons, are renowned for their exceptional thermal stability, chemical inertness, mechanical strength, and high surface area, making them suitable for advanced material applications. Metal–organic frameworks (MOFs), characterized by their porous crystalline structures, high surface area, and tunable porosity, have emerged as excellent candidates for gas adsorption and storage applications, particularly in the context of hydrogen. This paper explores the synthesis and properties of BNNs and MOFs, alongside the innovative approach of integrating BNNs within MOFs to create composite materials with synergistic properties. The integration of BNNs into MOFs enhances the overall thermal and chemical stability of the composite while improving hydrogen sensing and storage performance. Various synthesis methods for both BNNs and MOFs are discussed, including chemical vapor deposition, solvothermal synthesis, and in situ growth, with a focus on their scalability and reproducibility. Furthermore, the mechanisms underlying hydrogen sensing and storage are examined, including physisorption, chemisorption, charge transfer, and work function modulation. Electrochemical characterization techniques, such as cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge, are used to analyze the performance of BNN-MOF systems in hydrogen storage and sensing applications. These methods offer insights into the material’s electrochemical behavior and its potential to store hydrogen efficiently. Potential industrial applications of BNN-MOF composites are highlighted, particularly in fuel cells, hydrogen-powered vehicles, safety monitoring in hydrogen production and distribution networks, and energy storage devices. The integration of these materials can contribute significantly to the development of more efficient hydrogen energy systems. Finally, this study outlines key recommendations for future research, which include optimizing synthesis techniques, improving the hydrogen interaction mechanisms, enhancing the stability and durability of BNN-MOF composites, and performing comprehensive economic and environmental assessments. BNN-MOF composites represent a promising direction in the advancement of hydrogen sensing and storage technologies, offering significant potential to support the transition toward sustainable energy systems and hydrogen-based economies. Full article

This study describes the development of an optical-based surface plasmon resonance (SPR) aptasensor for the detection of cocaine. The aptasensor was prepared by first attaching gold nanoparticles to a clean SPR chip surface, followed by the addition of an aptamer to create a modified surface. This surface was characterized using contact angle and atomic force microscopy, revealing surface roughness values of 0.28 nm and 28.12 nm for the blank and modified surfaces, respectively. The detection of cocaine was carried out in the concentration range of 1 ng/mL to 1000 ng/mL, with a detection time of approximately 8 min and a cocaine limit of detection (LOD) of 0.43 ng/mL. Repeatability studies were conducted, and the stability of the signal response was examined at a concentration of 200 ng/mL. Adsorption isotherm models, including Scatchard, Langmuir, and Freundlich models, were calculated to assess the surface homogeneity of the SPR aptasensor chip, with the results indicating compatibility with the Langmuir isotherm model. Full article

Complexation between carnitine and acetylated or benzylated pyrogallol[4]arenes was studied in DMSO via dynamic NMR, UV-vis spectroscopy, and in the gas phase via electrospray ionization-mass spectrometry (ESI-MS). In the presence of benzylated tetra(phenyl)pyrogallol[4]arene, the interaction with carnitine via NMR was evident and was confirmed by means of UV-vis spectroscopy, where the formation of a host–guest-type complex was observed; this was stable and exhibited a change to a clear color. With benzylated tetra(propyl)pyrogallol[4]arene, the results showed that there was no interaction with the neurotransmitter. A plausible explanation for this behavior is based on the dynamic behavior of the benzylated tetra(propyl)pyrogallol[4]arene, and this shows the dependence on the size of the cavities and the substituent on the lower rim of the pyrogallo[4]arenes. Suitable crystals of O-acetylated-tetra(propyl)calix[4]pyrogallolarene were obtained and were characterized through an X-ray crystal structure determination. Full article

Three-dimensional printing technology has emerged as a versatile and cost-effective alternative for the fabrication of electrochemical sensors. To enhance sensor sensitivity and biocompatibility, a diverse range of biocompatible and conductive materials can be employed in these devices. This allows these sensors to be modified to detect a wide range of analytes in various fields. 3D-printed electrochemical sensors have the potential to play a pivotal role in personalized medicine by enabling the real-time monitoring of metabolite and biomarker levels. These data can be used to personalize treatment strategies and optimize patient outcomes. The portability and low-cost nature of 3D-printed electrochemical sensors make them suitable for point-of-care (POC) diagnostics. These tests enable rapid and decentralized analyses, aiding in diagnosis and treatment decisions in resource-limited settings. Among the techniques widely reported in the literature for 3D printing, the fused deposition modeling (FDM) technique is the most commonly used for the development of electrochemical devices due to the easy accessibility of equipment and materials. Focusing on the FDM technique, this review explores the critical factors influencing the fabrication of electrochemical sensors and discusses potential applications in clinical analysis, while acknowledging the challenges that need to be overcome for its effective adoption. Full article

The GPHF-Minilab™ is a portable toolkit for performing qualitative methods such as thin-layer chromatography (TLC) on common pharmaceuticals. It is particularly useful in resource-limited locations where it is more challenging to monitor for substandard and falsified (SF) medicines. However, the GPHF-Minilab™ TLC methods are only semi-quantitative at best and thus have issues monitoring product quality effectively. We have improved on the GPHF-Minilab™ TLC method for metronidazole, a common antibiotic, by making it fully quantitative. Sample solutions were spotted on TLC plates alongside three metronidazole standards at different concentrations. After development, plates were imaged in a lightbox with two different smartphone cameras. Images were processed through the open-source program ImageJ and resulting pixel data from the standard spots were used to create a calibration curve, enabling quantitation of the sample. The USP Metronidazole Tablet high-performance liquid chromatography (HPLC) assay was used as the reference method. We validated this TLC method using 250 and 500 mg metronidazole tablets from different manufacturers and assessed linearity, range, accuracy, precision, intermediate precision, specificity, and robustness. These improvements should enhance the GPHF-Minilab™ TLC methods for metronidazole product screening. Additionally, the procedure is extensible to other analytes, although further validation would be required for each Minilab method. Full article

This study examines the significant impact of bacterial, algal, and fungal toxins on foodborne illnesses, and stresses the importance of advanced detection techniques, such as high-performance liquid chromatography (HPLC)-based methodologies. It emphasizes the urgent need for further advancements in these techniques to ensure food safety, as they offer significant benefits, including low detection limits and the ability to be combined with other techniques to detect a wide range of toxins. In this regard, HPLC has emerged as a versatile and sensitive analytical technique for this purpose. Various HPLC methods, often enhanced with detectors such as ultraviolet (UV), fluorescence (FD), and mass spectrometry (MS), have been developed to identify and quantify microbial toxins in a wide variety of food samples. Recent advancements include HPLC-FD methods that utilize the natural fluorescence of certain aflatoxins, improving detection sensitivity. HPLC-MS/MS and UHPLC-MS/MS techniques offer high selectivity and sensitivity, making them suitable for detecting a wide range of toxins in trace quantities. The adaptability of HPLC, combined with innovative detection technologies and sample preparation methods, holds significant potential for enhancing food safety monitoring and reducing the global burden of foodborne diseases. Full article

Multidrug-resistant bacteria have complicated the treatment of gastrointestinal diseases; their microbial resistance stems from the indiscriminate use of medications and the transfer of resistance genes. Varronia curassavica Jacq., a plant traditionally used to treat rheumatic and gastrointestinal diseases in underserved populations, has sparked interest as a potential source of antimicrobial compounds. This study aimed to investigate the chemical composition and antibacterial effects of V. curassavica essential oil and to evaluate its toxicity in Drosophila melanogaster. The essential oil was extracted through hydrodistillation and its chemical composition was determined using GC-MS. Antibacterial tests were performed with microdilution. The results showed the presence of major compounds including α-pinene and β-caryophyllene. The essential oil did not show relevant MIC, but it enhanced the effects of the antibiotics, gentamicin, norfloxacin, and oxacillin. It exhibited no toxicity and did not affect geotaxis, even at high concentrations. The in silico analysis of α-pinene revealed low toxicity; however, its permeability to the BBB shows that caution is needed in its application. These results indicate that the essential oil of V. curassavica shows promising potential in enhancing pharmaceuticals to prevent increased bacterial resistance. In addition, it demonstrated safe aspects when tested on D. melanogaster. Full article

Optimizing forage quality is vital for enhancing animal performance and supporting the global animal production industry. Near-infrared (NIR) spectroscopy offers a rapid, non-destructive alternative to traditional, time-intensive laboratory analyses, enabling the on-site assessment of forage properties with significant advantages in cost, speed, and environmental impact. This review traces the development of NIR spectroscopy, outlines its core principles, and highlights its applications in animal nutrition. Additionally, it discusses the current technological state, challenges, and future prospects, emphasizing NIR’s growing role in promoting more sustainable and efficient animal production systems. Full article

A pressurized liquid extraction (PLE) method for the extraction of 31 organophosphate esters (OPEs) and novel organophosphate esters (NOPEs) has been developed. Unlike previously published methods, this method utilizes the high-throughput nature of PLE (as opposed to Soxhlet or sonication methods) without using potentially harmful organic solvents like methylene chloride. Combinations of hexane and acetone and hexane and ethyl acetate at various temperatures were examined. Extracts were concentrated and analyzed via gas chromatography–mass spectrometry. The final optimized method utilized 1:1 v/v hexane/ethyl acetate at 100 °C for three static cycles (5 min each) at 80% flush volume and a 100 s N₂ purge. This provided average surrogate corrected target analyte percent recoveries in spike and recovery experiments (n = 6) for OPEs and NOPEs of 106 ± 13%, with average surrogate recoveries of 88.6 ± 7.3%. The developed method was further validated using standard reference materials and was then applied to atmospheric particulate matter samples collected in the city of Providence, RI. The dataset reflected ambient concentrations of 16 OPEs and NOPEs (reported in pg m⁻³) for the first time in the greater Providence metropolitan area, including one of the first reports of NOPEs in atmospheric particulate matter in the U.S. Full article