Liquid phase microextraction techniques combined with chromatography analysis: A review

Sample pretreatment is the first and the most important step of an analytical procedure. In routine analysis, liquid-liquid microextraction (LLE) is the most widely used sample pre-treatment technique, whose goal is to isolate the target analytes, provide enrichment, with cleanup to lower the chemical noise, and enhance the signal. The use of extensive volumes of hazardous organic solvents and production of large amounts of waste make LLE procedures unsuitable for modern, highly automated laboratories, expensive, and environmentally unfriendly. In the past two decades, liquid-phase microextraction (LPME) was introduced to overcome these drawbacks. Thanks to the need of only a few microliters of extraction solvent, LPME techniques have been widely adopted by the scientific community. The aim of this review is to report on the state-of-the-art LPME techniques used in gas and liquid chromatography. Attention was paid to the classification of the LPME operating modes, to the historical contextualization of LPME applications, and to the advantages of microextraction in methods respecting the value of green analytical chemistry. Technical aspects such as description of methodology selected in method development for routine use, specific variants of LPME developed for complex matrices, derivatization, and enrichment techniques are also discussed

Solid phase microextraction techniques used for gas chromatography: A review

In the last decade, the development and adoption of greener and sustainable microextraction techniques have been proved to be an effective alternative to classical sample preparation procedures. In this review, 10 commercially available solid-phase microextraction systems are presented, with special attention to the appraisal of their analytical, bioanalytical, and environmental engineering. This review provides an overview of the challenges and achievements in the application of fully automated miniaturized sample preparation methods in analytical laboratories. Both theoretical and practical aspects of these environment-friendly preparation approaches are discussed. The application of chemometrics in method development is also discussed. We are convinced that green analytical chemistry will be really useful in the years ahead. The application of cheap, fast, automated, clever , and environmentally safe procedures to environmental, clinical, and food analysis will improve significantly the quality of the analytical data

Immobilization of γ-Glutamyl Transpeptidase from Equine Kidney for the Synthesis of Kokumi Compounds

γ-Glutamyl transpeptidase from equine kidney (ekGGT, E.C. 2.3.2.2) is an intrinsic membrane enzyme which transfers the γ-glutamyl moiety of glutathione to amino acids and peptides, thus producing γ-glutamyl derivatives. An immobilization study of ekGGT was carried out with the aim to develop a robust biocatalyst for the synthesis of γ-glutamyl amino acids which are known as kokumi compounds. Heterofunctional octyl-glyoxyl-agarose resulted in a high immobilization yield and activity recovery (93 % and 88 %, respectively). Immobilized ekGGT retained more than 95 % activity under reaction conditions (Tris-HCl, pH 9, 0.05 M) after 6 days, whereas the residual activity after 6 reaction cycles (18 days) was 85 %. The synthesis of γ-glutamylmethionine catalyzed by octyl-glyoxyl-agarose-ekGGT afforded the product in 42 % yield (101 mg). The immobilized ekGGT was characterized by Raman spectroscopy. The immobilization protocol developed for ekGGT could be of general applicability to membrane proteins

Immobilization of γ-Glutamyl Transpeptidase from Equine Kidney for the Synthesis of kokumi Compounds

\u3b3-Glutamyl transpeptidase from equine kidney (ekGGT, E.C. 2.3.2.2) is an intrinsic membrane enzyme which transfers the \u3b3-glutamyl moiety of glutathione to amino acids and peptides, thus producing \u3b3-glutamyl derivatives. An immobilization study of ekGGT was carried out with the aim to develop a robust biocatalyst for the synthesis of \u3b3-glutamyl amino acids which are known as kokumi compounds. Heterofunctional octyl-glyoxyl-agarose resulted in a high immobilization yield and activity recovery (93 % and 88 %, respectively). Immobilized ekGGT retained more than 95 % activity under reaction conditions (Tris-HCl, pH 9, 0.05 M) after 6 days, whereas the residual activity after 6 reaction cycles (18 days) was 85 %. The synthesis of \u3b3-glutamylmethionine catalyzed by octyl-glyoxyl-agarose-ekGGT afforded the product in 42 % yield (101 mg). The immobilized ekGGT was characterized by Raman spectroscopy. The immobilization protocol developed for ekGGT could be of general applicability to membrane proteins

Monitoring of air-dispersed formaldehyde and carbonyl compounds as vapors and adsorbed on particulate matter by denuder-filter sampling and gas chromatographic analysis

Carbonyl compounds (CCs) are products present both as vapors and as condensed species adsorbed on the carbonaceous particle matter dispersed in the air of urban areas, due to vehicular traffic and human activities. Chronic exposure to CCs is a potential health risk given the toxicity of these chemicals. The present study reports on the measurement of the concentrations of 14 CCs in air as vapors and 2.5 µm fraction PM by the ENVINT GAS08/16 gas/aerosol sampler, a serial sampler that uses annular denuder, as sampling device. The 14 CCs were derivatized during sampling prior to gas-chromatographic separation and multiple detection by mass spectrometry, nitrogen-phosphorus thermionic, electron capture detection. Outdoor air multiple samples were collected in four locations in the urban area of Florence. The results evidenced that formaldehyde, acetaldehyde, and acetone were the more abundant CCs in the studied areas. The data collected was discussed considering the particle to vapor ratio of each CC found. The CCs pollution picture obtained was tentatively related to the nature and intensity of the traffic transiting by the sampling sites. This approach allowed to determine 14 CCs in both concentrated and diluted samples and is proposed as a tool for investigating outdoor and indoor pollution

Application of Quality by Design Approach to Bioanalysis: Development of a Method for Elvitegravir Quantification in Human Plasma

Background: The application of Quality by Design (QbD) principles in clinical laboratories can help to develop an analytical method through a systematic approach, providing a significant advance over the traditional heuristic and empirical methodology. In this work, we applied for the first time the QbD concept in the development of a method for drug quantification in human plasma using elvitegravir as the test molecule. Methods: The goal of the study was to develop a fast and inexpensive quantification method, with precision and accuracy as requested by the European Medicines Agency guidelines on bioanalytical method validation. The method was divided into operative units, and for each unit critical variables affecting the results were identified. A risk analysis was performed to select critical process parameters that should be introduced in the design of experiments (DoEs). Different DoEs were used depending on the phase of advancement of the study. Results: Protein precipitation and high-performance liquid chromatography-tandem mass spectrometry were selected as the techniques to be investigated. For every operative unit (sample preparation, chromatographic conditions, and detector settings), a model based on factors affecting the responses was developed and optimized. The obtained method was validated and clinically applied with success. Conclusions: To the best of our knowledge, this is the first investigation thoroughly addressing the application of QbD to the analysis of a drug in a biological matrix applied in a clinical laboratory. The extensive optimization process generated a robust method compliant with its intended use. The performance of the method is continuously monitored using control charts