Critical overview of selected contemporary sample preparation techniques

Present state and applications of single drop microextraction for the determination of harmful organic compounds and pollutants

Single drop microextraction (SDME) nowadays earns an increasing attention by scientists due to its simplicity, low cost and the need for only common laboratory equipment. This microextraction technique combines sample cleanup and pre-concentration of analytes in one step. Furthermore, a significant reduction in the amount of organic solvents needed comparing to standard LLE techniques places SDME into the position of environmental friendly extraction techniques. SDME is a straightforward technique in which a micro-drop of solvent is suspended from the tip of a conventional micro-syringe and then it is in a direct contact with a sample solution in which it is immiscible or it could be suspended in the headspace above the sample. The paper overviews developments of the state-of-the-art SDME techniques for the extraction of harmful organic compound and pollutants from environmental, food and biological matrices. Key extraction parameters essential for SDME performance were described and discussed.

Application of the QuEChERS procedure for analysis of Δ9-tetrahydrocannabinol and its metabolites in authentic whole blood samples by GC-MS/MS

Purpose

Analysis of drugs and their metabolites in biofluids usually demands the application of sample preparation methods that allow for full isolation of analyzed substances from the matrix. The purpose of this study was to develop a method using the QuEChERS procedure for analysis of Δ⁹-tetrahydrocannabinol (THC), 11-hydroxy-Δ⁹-tetrahydrocannabinol (11-OH-THC) and 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol (11-COOH-THC).

Methods

THC, 11-OH-THC and 11-COOH-THC were quantified in whole blood samples using QuEChERS extraction and gas chromatography–tandem mass spectrometry.

Results

The described method is characterized by good linearity, very low detection limits and satisfactory inter- and intraday precisions for THC, 11-OH-THC and 11-COOH-THC. The applicability of the procedure was confirmed using authentic whole blood samples collected from 30 persons suspected of driving under the influence of drugs.

Conclusions

The application of QuEChERS extraction described herein is a simple and convenient method for the routine analysis of THC, 11-OH-THC and 11-COOH-THC in whole blood samples from living and deceased humans. To our knowledge, this paper is the first academic report describing the QuEChERS extraction of THC and its metabolites from whole blood specimens.

Current state of bioanalytical chromatography in clinical analysis

Chromatographic methods have become popular in clinical analysis in both routine and research laboratories.

Use of solid phase microextraction to identify volatile organic compounds in brazilian wines from different grape varieties

Abstract The Brazilian wine industry has shown significant growth in recent years and the insertion of new concepts, such as geographical indications as signs of quality, has placed Brazil in tune with the tendencies of world wine production. The aim of this work was to apply the Solid Phase Microextraction technique in combination with Gas Chromatography-Mass Spectrometry to study Brazilian wines made from different grape varieties, in order to separate and identify their volatile organic compounds. These substances were identified by comparisons between the spectra obtained with those presented in the NIST library database, and by comparisons with linear retention indices and literature data. The amounts of the compounds were calculated based on the total peak areas of the chromatograms. Forty-seven volatile compounds were identified and grouped into alcohols, aldehydes, fatty acids, esters, hydrocarbons, ketones and terpenes. Most of them belonged to the ester function, conferring a fruity aroma on the wines. The alcohols may have originated from the yeast metabolism, contributing to the alcoholic and floral aromas. Ethyl lactate, 1-hexanol and diethyl maleate were identified in all the varieties, except Merlot. Decanal, methyl citronellate, (E)-2-hexenyl-3-methylbutyrate were only found in Merlot, while 2,3-butanediol was only present in the Tannat wines. 2-Phenylethanol was present in all varieties and is recognized as giving pleasant rose and honey attributes to wines. This study showed that the volatile profile of red wines is mainly characterized by esters and higher alcohols. The statistical analysis of the comparison of averages showed a greater amount of averages significantly different in the relative areas of Merlot wine. The Principal Component Analysis showed one grouping composed only of the Merlot wine samples, and this was probably related to the existence of the volatile organic compounds that were specifically identified in these wines.

Determination of genotoxic epoxide at trace level in drug substance by direct injection GC/MS

A novel direct injection gas chromatography method coupled with selective ion monitoring mass spectrometry (GC/SIM-MS) was developed for quantitation of trace levels of high boiling point (HBP) epoxide genotoxic impurity (GTI) in drug substance. The injector temperature was optimized with the aims to minimize matrix effects and enhance SIM signal response. The final injector temperature 160°C was selected after balancing between these two factors. The column screening was conducted as well and MN OPTIMA delta-3 silica capillary column was selected since it showed good peak symmetry without column bleeding. The good linearity was established for the concentration in the range from 0.0045μg/mL to 0.5μg/mL with a R²=0.9999. The limit of detection (LOD) and the limit of quantitation (LOQ) were 0.0014μg/mL and 0.0045μg/mL, respectively. The recovery which ranged from 95.0% to 112.5% could meet the ICH acceptance criteria. The validation results demonstrated the good linearity, precision and accuracy of the method which can be further adopted as an adequate quality control tool for quantitation of epoxide impurity at trace levels in drug substance and drug product.

Micro-SPE in pipette tips as a tool for analysis of small-molecule drugs in serum

AIM

Micro-SPE in pipette tips (μ-SPE-PT) with particle sorbent has never been used in small-molecule drug analysis. Methodology & results: μ-SPE-PT was used for the extraction of statins from biological materials followed by UHPLC-MS/MS. The commercial and homemade μ-SPE-PT tips filled with particle sorbent were compared. While the homemade tips enabled direct serum sample loading into the sorbent, protein precipitation (PP) had to be implemented before μ-SPE-PT procedure using commercial tips. Three μ-SPE-PT methods were developed and validated: method A: μ-SPE-PT with homemade tips; method B: PP + μ-SPE-PT with homemade tips; and method C: PP + μ-SPE-PT with commercial tips. Method A enabled a simple high-throughput approach (48 samples in 90 min) compared with methods B and C that required three-times longer time. However, PP increased the recoveries of protein-bound analytes and extracts purity in methods B and C. The matrix effects without internal standards correction for method C were significantly higher than those for the methods A and B.

CONCLUSION

Compared with commercial tips, homemade tips filled with particles were found to be more suitable for drug analysis. Commercial tips tested in this study were found challenging but the conditions under which they could be applicable were also defined.

Simultaneous assay of multiple antibiotics in human plasma by LC-MS/MS: importance of optimizing formic acid concentration

AIM

Optimal dosing of antibiotics in critically ill patients is complicated by the development of resistant organisms requiring treatment with multiple antibiotics and alterations in systemic exposure due to diseases and extracorporeal drug removal. Developing guidelines for optimal antibiotic dosing is an important therapeutic goal requiring robust analytical methods to simultaneously measure multiple antibiotics.

METHODS

An LC-MS/MS assay using protein precipitation for cleanup followed by a 6-min gradient separation was developed to simultaneously determine five antibiotics in human plasma.

RESULTS

The precision and accuracy were within the 15% acceptance range. The formic acid concentration was an important determinant of signal intensity, peak shape and matrix effects.

CONCLUSION

The method was designed to be simple and successfully applied to a clinical pharmacokinetic study.

Determination of N-nitrosodiethanolamine in cosmetic products by reversed-phase dispersive liquid-liquid microextraction followed by liquid chromatography

A new analytical method for the determination of N-nitrosodiethanolamine (NDELA), a very harmful compound not allowed in cosmetic products, is presented. The method is based on a new approach of dispersive liquid-liquid microextraction (DLLME) useful for extraction of highly polar compounds, called reversed-phase DLLME (RP-DLLME), followed by liquid chromatography-ultraviolet/visible (LC-UV/Vis) determination. The variables involved in the RP-DLLME process were studied to provide the best enrichment factors. Under the optimized conditions, a mixture of 750µL of acetone (disperser solvent) and 125µL of water (extraction solvent) was rapidly injected into 5mL of toluene sample solution. The extracts were injected into the LC-UV/Vis system using ammonium acetate 0.02M as mobile phase. After chromatographic separation, the eluate passed throughout a photolysis unit in order to convert NDELA to nitrite, and then it was merged with a flow stream of Griess Reagent and passed throughout a post-column reactor at 50°C to derivatize nitrite into an azo-dye, which was finally measured spectrophotometrically at 540nm. The method was successfully validated showing good linearity, an enrichment factor of 31.5±0.9, limits of detection and quantification of 1.1 and 3.6ngmL^-1, respectively, and a good repeatability (RSD <8%). Finally, the proposed analytical method was applied to the determination of NDELA in commercial cosmetic samples of different nature, specifically three lipophilic creams and a hydrophilic shower gel, with good relative recovery values (87 - 117%) thus showing that matrix effects are negligible. These results were compared with those obtained by applying the ISO 10130 official method, which uses the same detection approach. It was concluded that a great improvement in the sensitivity was achieved, whereas the use of organochlorine solvents is avoided and therefore it can be considered as a greener approach.

Online Extraction Coupled to Liquid Chromatography Analysis (OLE-LC): Eliminating Traditional Sample Preparation Steps in the Investigation of Solid Complex Matrices

Current methods employed for the analysis of the chemical composition of solid matrices (such as plant, animal, or human tissues; soil; etc.) often require many sample treatment steps, including an extraction step with exclusively dedicated solvents. This work describes an optimized analytical setup in which the extraction of a solid sample is directly coupled to its analysis by high-performance liquid chromatography. This approach avoids (i) the use of pumps and valves other than those comprising the HPLC instrument, (ii) the use of solvents other than those of the mobile phase, and (iii) the need to stop the mobile phase flow at any time during the full analytical procedure. The compatibility of this approach with the direct analysis of fresh tissues (leaves, stems, and seeds of four plant species with dissimilar chemical compositions) was successfully demonstrated, leading to the elimination of sample preparation steps such as drying, grinding, concentration, dilution, and filtration, among others. This work describes a new, simple, and efficient green approach to minimize or eliminate sample treatment procedures. It could be easily applied for quality control of plant materials and their derived products through chromatographic fingerprints and for untargeted metabolomic investigations of solid matrices, among other applications.

Current trends in sample preparation for cosmetic analysis

The widespread applications of cosmetics in modern life make their analysis particularly important from a safety point of view. There is a wide variety of restricted ingredients and prohibited substances that primarily influence the safety of cosmetics. Sample preparation for cosmetic analysis is a crucial step as the complex matrices may seriously interfere with the determination of target analytes. In this review, some new developments (2010-2016) in sample preparation techniques for cosmetic analysis, including liquid-phase microextraction, solid-phase microextraction, matrix solid-phase dispersion, pressurized liquid extraction, cloud point extraction, ultrasound-assisted extraction, and microwave digestion, are presented. Furthermore, the research and progress in sample preparation techniques and their applications in the separation and purification of allowed ingredients and prohibited substances are reviewed.

Bioanalytical challenge: A review of environmental and pharmaceuticals contaminants in human milk

An overview of bioanalytical methods for the determination of environmental and pharmaceutical contaminants in human milk is presented. The exposure of children to these contaminants through lactation has been widely investigated. The human milk contains diverse proteins, lipids, and carbohydrates and the concentration of these components is drastically altered during the lactation period providing a high degree of an analytical challenge. Sample collection and pretreatment are still considered the Achilles' heel. This review presents liquid chromatographic methods developed in the last 10 years for this complex matrix with focuses in the extraction and quantification steps. Green sample preparation protocols have been emphasized.

Evaluation of alternative sorbents for dispersive solid-phase extraction clean-up in the QuEChERS method for the determination of pesticide residues in rice by liquid chromatography with tandem mass spectrometry

Many compounds are used for pest control during the production and storage of rice, making it necessary to employ multiclass methods for pesticide residues determination. For this purpose, QuEChERS-based methods are very efficient, fast and accurate, and improvements in the clean-up step are important, especially for complex matrices, like cereals. In this work, different sorbents such as chitosan, florisil(®) , alumina, diatomaceous earth, graphitized carbon black, besides the commonly used primary secondary amine and octadecylsilane, were evaluated for dispersive solid-phase extraction clean-up in acetate-buffered QuEChERS method for the determination of residues of 20 representative pesticides and one metabolite in rice by liquid chromatography coupled to tandem mass spectrometry. The sorbent C18 presented the best results, however, chitosan showed similar results, and the best performance among the unconventional sorbents evaluated. The method limit of quantification, attending accuracy (70-120% recovery) and precision (RSD ≤20%) criteria, ranged from 5 to 20 μg/kg. Results showed that chitosan is an effective alternative to reduce analysis costs, maintaining the method reliability and accuracy.

Positive lists of cosmetic ingredients: Analytical methodology for regulatory and safety controls - A review

Cosmetic products placed on the market and their ingredients, must be safe under reasonable conditions of use, in accordance to the current legislation. Therefore, regulated and allowed chemical substances must meet the regulatory criteria to be used as ingredients in cosmetics and personal care products, and adequate analytical methodology is needed to evaluate the degree of compliance. This article reviews the most recent methods (2005-2015) used for the extraction and the analytical determination of the ingredients included in the positive lists of the European Regulation of Cosmetic Products (EC 1223/2009): comprising colorants, preservatives and UV filters. It summarizes the analytical properties of the most relevant analytical methods along with the possibilities of fulfilment of the current regulatory issues. The cosmetic legislation is frequently being updated; consequently, the analytical methodology must be constantly revised and improved to meet safety requirements. The article highlights the most important advances in analytical methodology for cosmetics control, both in relation to the sample pretreatment and extraction and the different instrumental approaches developed to solve this challenge. Cosmetics are complex samples, and most of them require a sample pretreatment before analysis. In the last times, the research conducted covering this aspect, tended to the use of green extraction and microextraction techniques. Analytical methods were generally based on liquid chromatography with UV detection, and gas and liquid chromatographic techniques hyphenated with single or tandem mass spectrometry; but some interesting proposals based on electrophoresis have also been reported, together with some electroanalytical approaches. Regarding the number of ingredients considered for analytical control, single analyte methods have been proposed, although the most useful ones in the real life cosmetic analysis are the multianalyte approaches.

Preparation of magnetic nanographene sorbent for extraction and quantification of targeted PPCPs in environmental water samples

Nano MGO provides the advantages of large surface area and reusability property for enrichment of selected PPCPs.

The Progress of Metabolomics Study in Traditional Chinese Medicine Research

Traditional Chinese medicine (TCM) has played important roles in health protection and disease treatment for thousands of years in China and has gained the gradual acceptance of the international community. However, many intricate issues, which cannot be explained by traditional methods, still remain, thus, new ideas and technologies are needed. As an emerging system biology technology, the holistic view adopted by metabolomics is similar to that of TCM, which allows us to investigate TCM with complicated conditions and multiple factors in depth. In this paper, we tried to give a timely and comprehensive update about the methodology progression of metabolomics, as well as its applications, in different fields of TCM studies including quality control, processing, safety and efficacy evaluation. The herbs investigated by metabolomics were selected for detailed examination, including Anemarrhena asphodeloides Bunge, Atractylodes macrocephala Kidd, Pinellia ternate, etc.; furthermore, some valuable results have been obtained and summarized. In conclusion, although the study of metabolomics is at the early phase and requires further scrutiny and validation, it still provides bright prospects to dissect the synergistic action of multiple components from TCM. Overall, with the further development of analytical techniques, especially multi-analysis techniques, we expect that metabolomics will greatly promote TCM research and the establishment of international standards, which is beneficial to TCM modernization.