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PubMed2006

Trends in solventless sample preparation techniques for environmental analysis.

The paper presents recent trends in solventless sample preparation techniques for environmental analysis. First, a general classification of solventless methods is given. Next, three of them, treated as preferable techniques, i.e. SPME, SDME and HS, are presented in detail, with respect to their usability and effectiveness for environmental samples. Examples of all discussed techniques are given in the tables.

Chromatography↗
PubMed2006

Sampling volatile compounds from natural products with headspace/solid-phase micro-extraction.

Recent advances in the development of analytical methods based on headspace/solid-phase micro-extraction (HS/SPME) of natural aroma compounds are reviewed, with special emphasis on increasing reproducibility. Representative examples of applications of HS/SPME to the determination of components at trace levels, strategies for fiber selection, and improvement of SPME sampling conditions are presented. Examples of applications to quality control and sample classification, based on aroma profiling were selected to highlight the use of multivariate statistical methods.

Biological Products↗
PubMed2006

Automated sample treatment by flow techniques prior to liquid-phase separations.

Sample preparation (SP) is an integral and important part of an analytical process. Lately, SP has been the topic of increased interest in research and development of novel advanced technologies. Major needs in this aspect are miniaturization, automation, and enrichment. Among other methodologies, flow techniques can be conveniently and effectively coupled to liquid-phase separation technologies for on-line sample preparation. This paper reviews the current trends in on-line automated sample preparation by flow-through techniques prior to liquid-phase separations. Strategies and interfaces developed to couple flow techniques with liquid chromatography, capillary electrophoresis, and mass spectrometry are described. Advantages and limitations of the coupling are discussed. The paper also highlights certain selected applications of these coupled systems.

Chromatography, Liquid↗
PubMed2006

Ultrasound-assisted digestion: a useful alternative in sample preparation.

Ultrasound-assisted digestion is a promising alternative in the analysis of solid samples when either simple dissolution or direct analysis is not applicable. However, the field of application of ultrasonic sample digestion is still small in comparison with classical digestion alternatives and, particularly, with microwave-assisted digestion. This fact can be justified by the scant knowledge analytical chemists have about the advantages ultrasonic energy provides to digestion. Among these, the strict control at low temperatures of ultrasound applications allows the implementation of ultrasonic-assisted steps in biochemical analyses. In this connection, two specific biological applications, ultrasonic enzymatic digestion and assistance of ultrasound for cell disruption, are also reviewed.

Cell Fractionation↗
PubMed2006

Techniques of preparing plant material for chromatographic separation and analysis.

This paper discusses preparation techniques of samples of plant material for chromatographic analysis. Individual steps of the procedures used in sample preparation, including sample collection from the environment or from tissue cultures, drying, comminution, homogenization, leaching, extraction, distillation and condensation, analyte enrichment, and obtaining the final extracts for chromatographic analysis are discussed. The techniques most often used for isolation of analytes from homogenized plant material, i.e., Soxhlet extraction, ultrasonic solvent extraction (sonication), accelerated solvent extraction, microwave-assisted extraction, supercritical-fluid extraction, steam distillation, as well as membrane processes are emphasized. Sorptive methods of sample enrichment and removal of interferences, i.e., solid-phase extraction, and solid-phase micro-extraction are also discussed.

Chromatography↗
PubMed2006

Determination of drugs in biological fluids by direct injection of samples for liquid-chromatographic analysis.

The analysis of drugs in various biological fluids is an important criterion for the determination of the physiological performance of a drug. After sampling of the biological fluid, the next step in the analytical process is sample preparation. The complexity of biological fluids adds to the challenge of direct determination of the drug by chromatographic analysis, therefore demanding a sample preparation step that is often time-consuming, tedious, and frequently overlooked. However, direct on-line injection methods offer the advantage of reducing sample preparation steps and enabling effective pre-concentration and clean-up of biological fluids. These procedures can be automated and therefore reduce the requirements for handling potentially infectious biomaterial, improve reproducibility, and minimize sample manipulations and potential contamination. The objective of this review is to present an overview of the existing literature with emphasis on advances in automated sample preparation methods for liquid-chromatographic methods. More specifically, this review concentrates on the use of direct injection techniques, such as restricted-access materials, turbulent-flow chromatography and other automated on-line solid-phase extraction (SPE) procedures. It also includes short overviews of emerging automated extraction-phase technologies, such as molecularly imprinted polymers, in-tube solid-phase micro-extraction, and micro-extraction in a packed syringe for a more selective extraction of analytes from complex samples, providing further improvements in the analysis of biological materials. Lastly, the outlook for these methods and potential new applications for these technologies are briefly discussed.

Body Fluids↗
PubMed2006

Liquid-phase micro-extraction techniques in pesticide residue analysis.

Modern trends in analytical chemistry are towards the simplification and miniaturization of sample preparation, as well as the minimization of organic solvent used. In view of this aspect, several novel micro-extraction techniques are being developed in order to reduce the analysis step, increase the sample throughput and to improve the quality and the sensitivity of analytical methods. One of the emerging techniques in this area is liquid-phase micro-extraction (LPME). It is a miniaturized implementation of conventional liquid/liquid extraction (LLE) in which only microliters of solvents are used instead of several hundred milliliters in LLE. It is quick, inexpensive and can be automated. In the last few years, LPME has been combined with liquid chromatography (LC) and capillary electrophoresis (CE), besides the generally used coupling to gas chromatography (GC), and has been applied to various matrices, including biological, environmental, and food samples. This work is aimed at providing an overview of the major developments of LPME, coupled with chromatography and CE, as reported in the literature. The paper will focus on the application of the technique to different matrices and the aim is to reveal the panorama of opportunities and to try to indicate the potential of LPME in pesticide analysis. A critical review of the first applications to pesticide analyses is presented in the main part of the manuscript. The optimization of LPME as well as advantages and disadvantages are discussed. It is concluded that, because of its high pre-concentration factor, LPME can be introduced with benefit into water analysis for several pesticide groups. In particular, the application of LPME to non-polar pesticides in environmental analysis appears to be promising. However, similar to other micro-extraction techniques, such as solid phase micro-extraction (SPME), serious limitations still remain when analyzing semi-solid and solid environmental, food or biological matrices and/or highly polar compounds. Thus, other pre-concentration techniques may be a good alternative if an analytical problem cannot be sufficiently dealt with LPME.

Chromatography, Liquid↗
PubMed2006

The essence of DNA sample preparation for MALDI mass spectrometry.

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has become an important analytical technique in nucleic acid research. MALDI is used for quality control of oligonucleotides as well as for analyzing DNA markers. Sample preparation of nucleic acids is crucial for obtaining high-quality mass spectra. Sample purity, solvent content, suitable matrices, and substrate surfaces, as well as laboratory conditions affect spectra quality. This review presents essential information with regard to sample preparation, DNA modification chemistry, and DNA purification, along with a discussion of instrumental advances, which facilitate and extend the applicability of MALDI in genomics.

Chromatography↗
PubMed2006

Role of carbon nano-materials in the analysis of biological materials by laser desorption/ionization-mass spectrometry.

At present, carbon nano-materials are being utilized in various procedures, especially in laser desorption/ionization-mass spectrometry (LDI-MS) for analyzing a range of analytes, which include peptides, proteins, metabolites, and polymers. Matrix-oriented LDI-MS techniques are very well established, with weak organic acids as energy-absorbing substances. Carbon materials, such as nano-tubes and fullerenes are being successfully applied in the small-mass range, where routine matrices have strong background signals. In addition, the role of carbon nano-materials is very well established in the fractionation and purification fields. Modified diamond powder and surfaces are utilized in binding peptides and proteins from complex biological fluids and analyzed by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS). Polylysine-coated diamond is used for solid-phase extraction to pre-concentrate DNA oligonucleotides. Graphite is useful for desalting, pre-concentration, and as energy-absorbing material (matrix) in desorption/ionization. Carbon nano-tubes in their different derivatized forms are used as matrix materials for the analysis of a range of analytes, such as carbohydrates, amino acids, peptides, proteins, and some environmental samples by LDI-MS. Fullerenes are modified in different ways to bind serum entities analyzed through MALDI/TOF-MS and are subsequently utilized in their identifications. In addition, the fullerenes are a promising matrix in LDI-MS, but improvements are needed.

Biological Products↗
PubMed2006

Chromatography-based on- and in-line pre-concentration methods in capillary electrophoresis.

Capillary electrophoresis (CE) poses unique challenges in many different analytical applications, mainly to biological and complex samples and when only small amounts of sample are available, due to its low sample consumption. As a consequence, poor limits of detection are usually observed with this technique, especially with UV photodetectors. Minimal or no sample treatment is desirable in any analytical method to avoid external sources of contamination or errors and to provide a high throughput. On- and in-capillary sample pre-concentration strategies, based on solid-phase extraction (SPE) technology can take advantage of both techniques (SPE and CE), while avoiding sample contamination and tedious manipulations when the sample amount is an issue. Moreover, the combination can provide two-dimensional separations. This review collects the most recent strategies that merge SPE technology built on- and in-capillary pre-concentration for increasing sensitivity and/or selectivity.

Chromatography↗
PubMed2006

Evaluation of automated micro solid phase extraction tips (micro-SPE) for the validation of a LC-MS/MS bioanalytical method.

Automated micro-SPE tips were successfully utilized for the determination of posaconazole in rat plasma. The bioanalytical method using micro-SPE tips was successfully qualified for routine quantitation of posaconazole over the concentration range of 10.0-10,000 ng/mL in rat EDTA plasma. Inter-assay precision, based on percent relative deviation for n=18 replicate quality controls, was < or =5.7%. Inter-assay accuracy based on n=18 replicate quality controls was +/-7.7%. Complete solid phase extraction using micro-SPE tips was demonstrated on a Tomtec liquid handler where >95% recovery for posaconazole was obtained. The micro-SPE tips had sufficient capacity to extract at least 100 microL plasma fortified with 10 microg/mL of posaconazole and the analyte could be efficiently eluted with as little as 60 microL of methanol. Of particular note is the unique ability of these micro-SPE tips to perform exhaustive solid phase extraction more commonly performed when using liquid/liquid extraction.

Animals↗
PubMed2002

Cozart Rapiscan system: our experience with saliva tests.

International literature has devoted many contributions to the evaluation of alternative biological matrices (such as saliva) as diagnostic tools in drug testing. The immunoassay Cozart Rapiscan saliva drug system, has been studied in recent years. In the present paper we report our experience with saliva collection and the quali-quantitative determination of drugs of abuse. Fifty-nine saliva samples were collected by the Cozart Rapiscan pad. Qualitative analyses were carried out by Cozart Rapiscan System and the results were confirmed by a solid-phase microextraction-GC-MS technique. Quantitative determinations were performed for methadone and its metabolite by GC-MS technique. The Cozart System provides collection and transfer procedures more easily than other systems, requiring minimal operator intervention.

Gas Chromatography-Mass Spectrometry↗
PubMed2005

High-performance SPME/AP MALDI system for high-throughput sampling and determination of peptides.

This paper presents the performance characteristics for a new multiplexed solid-phase microextraction/atmospheric pressure matrix-assisted laser desorption/ionization (SPME/AP MALDI) source configuration for a hybrid quadrupole-linear ion trap instrument. The results demonstrate that thorough optimization of parameters such as SPME coating material, optics configurations, extraction solvents, and fiber capacity provides dramatic sensitivity improvements (>1000x) over previous reports in the literature. The multiplexed SPME plate is capable of simultaneous extraction from 16 different wells on a multiwell plate, eliminating the need for extensive sample preparation. Subfemtomole sensitivity is demonstrated for peptide standards and protein digests with run-run reproducibility ranging from approximately 13 to 31%. This high-performance SPME/AP MALDI system shows potential for high-throughput extraction from biological samples.

Angiotensin I↗
PubMed2005

Distribution and mass inventory of total dichlorodiphenyldichloroethylene in the water column of the southern California bight.

A large-scale survey on the area and depth stratified distribution of dichlorodiphenyltrichloroethane (DDT; mainly p,p'- and o,p'-dichlorodiphenyldichloroethylene (DDE)) contamination in the water column of the Southern California Bight (SCB) was conducted in 2003-2004 using a solid-phase microextraction-based sampling technique. Dissolved-phase DDEs were clearly widespread, with the central SCB containing the highest levels, and the Palos Verdes Shelf sediments have remained the dominant source of DDT compounds to the SCB. The p,p'- and o,p'-DDE concentrations ranged from < 0.073 to 2.6 ng/L and from < 0.043 to 0.26 ng/L, respectively, clearly elevated with respect to measured values from across the globe. DDEs were hypothesized to have been transported from the historically contaminated zone on the Palos Verdes Shelf to other areas via a repeated process of sediment resuspension/deposition and short-range advection. Total mass inventories were estimated at 14 and 0.86 kg for p,p'- and o,p'-DDE, respectively, for the sampled area, resulting in p,p'- and o,p'-DDE mass inventories for the entire SCB of 230 and 14 kg, respectively. Furthermore, total fluxes of p,p'-DDE were estimated to be in the range of 0.8 to 2.3 metric tons per year. These results suggest that the SCB has been and continues to be a significant source of DDT contamination to the global oceans.

California↗
PubMed2003

Use of the enantiomeric composition for the assessment of the authenticity of fruit beverages.

Enantiomeric compositions of chiral terpenes in commercial fruit beverages were examined by solid phase microextraction-gas chromatography (SPME-GC). Optimization of the method was accomplished on the basis of some parameters involved in the extraction, such as heating temperature and extraction time, that provided the highest peak areas, 60 degrees C and 2 min being the optimal values. With the proposed method relative standard deviation (RSD) values from three replicates ranging from 2 to 12% were obtained. The enantiomeric distribution of some terpenes remained constant, whereas other terpenes (linalool, terpinen-4-ol, and alpha-terpineol) exhibited a considerable variation among samples. This can be indicative of the eventual addition of aromas to some fruit beverages.

Acyclic Monoterpenes↗
PubMed2003

ELISA for monitoring lipid oxidation in chicken myofibrils through quantification of hexanal-protein adducts.

The objectives of this study were to optimize a monoclonal competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) for hexanal detection, optimize solubilization and alkylation procedures for the formation of hexanal-protein adducts, and compare the ability the CI-ELISA, thiobarbituric acid reactive substances assay (TBARS), and a solid-phase microextraction-gas chromatography-mass spectrometry (GC/MS-SPME) method for monitoring lipid oxidation in freeze-dried chicken protein. Freeze-dried myofibrils with added methyl linoleate (0.6 mmol/g of protein) were stored at 50 degrees C at two water activities (a(w) = 0.30 and 0.75) for 5 days. Hexanal was measured by GC/MS-SPME and CI-ELISA, and malonaldehyde by TBARS. At an a(w) of 0.30, 34.7 and 39.7 microg of hexanal/g of myofibril were detected by GC/MS-SPME and CI-ELISA, respectively, after 4 days of storage. At an a(w) of 0.75, 39.8 and 61.1 microg of hexanal/g of myofibril were detected by GC/MS-SPME and CI-ELISA, respectively, after 4 days of storage. The CI-ELISA was well correlated with the GC/MS-SPME (r = 0.78) and TBARS (r = 0.87) methods. The correlation of the hexanal-specific CI-ELISA to both GC/MS-SPME and TBARS verified the ability of the CI-ELISA to be used as an index of lipid oxidation, offering the convenience for use in a kit to be utilized within a food-processing facility.

Aldehydes↗
PubMed2004

Evaluation of the antimicrobial activity of citrus essences on Saccharomyces cerevisiae.

The aim of this research was to assess the antimicrobial activity of nine different industrial essences used in a soft drink factory in relation to their composition, as well as to verify the role of vapor pressure on their bioactivity. The essences were tested against a Saccharomyces cerevisiae strain isolated from spoiled soft drinks. The tests were carried out by adding the essences directly to a liquid medium or into the headspace of closed systems inoculated with the yeast. The headspace composition was evaluated through a solid phase microextraction-gas chromatography technique. The use of a mass spectrometer allowed the identification of the peaks detected. The microbial growth was indirectly monitored by measuring the metabolic CO2 released by the yeast. The results obtained indicated that the most effective essences were characterized by the highest concentration of some terpenes, such as citral, beta-pinene, and p-cymene. Moreover, all of the essences were more bioactive when added directly to the liquid medium.

Citrus↗
PubMed2004

Hydrolysis of glycosidically bound volatiles from apple leaves (Cv. Anna) by Aspergillus niger beta-glucosidase affects the behavior of codling moth (Cydia pomonella L.).

Glycosidically bound volatiles released from apple leaf extracts (cv. Anna) were analyzed by solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and their behavioral effects on codling moth (CM) adults were evaluated in cage bioassays. The levels of 1-octanol, linalool, geraniol, benzyl alcohol, methyl salicylate, (2R,5R)-theaspirane, and (2S,5R)-theaspirane were significantly increased in the leaf extracts containing the Aspergillus niger beta-glucosidase (BGL1) compared to the extracts containing the glucoimidazole. The attractiveness of individual compounds to CM adults was found in the following decreasing order: methyl salicylate and mixture of two theaspirane isomers, followed by linalool and benzyl alcohol. Geraniol was found to be repellent to CM adults. The addition of geraniol (39.4 ng mL(-1)) to any of the individual volatiles or to a mixture of these attractants eliminated their attractiveness. Our data suggest the possible application of geraniol as a repellent and methyl salicylate or theaspiranes as attractants for the integrated control of CM in apple orchards.

Acyclic Monoterpenes↗