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PubMed2000

Solid-phase microextraction in pesticide residue analysis.

The applications of solid-phase microextraction (SPME) for sample preparation in pesticide residue analysis are reviewed in this paper taking into account the different approaches of this technique coupled mainly to gas chromatography but also to high-performance liquid chromatography. A complete revision of the existing literature has been made considering the different applications divided according to the pesticide families (organochlorine, organophosphorus, triazines, thiocarbamates, substituted uracils, urea derivatives and dinitroanilines among others) and the sample matrices analysed which included environmental samples (water and soil), food samples and biological fluids. Details on the analytical characteristics of the procedures described in the reviewed papers are given, and new trends in the applications of SPME in this field are discussed.

Chromatography, Gas↗
PubMed2000

Solid-phase microextraction in the determination of methadone in human saliva by gas chromatography-mass spectrometry.

Solid-phase microextraction (SPME) with a 100-microm polydimethylsiloxane film fiber was applied to the determination of methadone and 2-ethylidine-3,3-diphenylpyrrolidine (EDDP) by GC-MS in human saliva and compared with liquid-liquid extraction. A shorter extraction time of 30 min with the fiber was obtained, speeding up the total analysis time. Linearity was found for SPME from 0.05 to 2.0 microg/mL (r = 0.9976 for methadone; r = 0.9988 for EDDP) with precision between 0.7 and 4.3% for saliva spiked with 0.2 and 1.5 microg/mL of methadone and EDDP. The limit of detection using SPME was 0.04 microg/mL for methadone and 0.008 microg/mL for EDDP. Analytical recoveries of SPME and liquid-liquid extraction ranged from 98.8 to 103.6%. The use of deuterated internal standard by both methods have yielded comparable results. Thus, the SPME method is highly accurate, precise, and useful for determination of methadone and EDDP in saliva.

Dimethylpolysiloxanes↗
PubMed2004

Solid-phase microextraction: a powerful sample preparation tool prior to mass spectrometric analysis.

Sample preparation is an essential step in analysis, greatly influencing the reliability and accuracy of resulted the time and cost of analysis. Solid-Phase Microextraction (SPME) is a very simple and efficient, solventless sample preparation method, invented by Pawliszyn in 1989. SPME has been widely used in different fields of analytical chemistry since its first applications to environmental and food analysis and is ideally suited for coupling with mass spectrometry (MS). All steps of the conventional liquid-liquid extraction (LLE) such as extraction, concentration, (derivatization) and transfer to the chromatograph are integrated into one step and one device, considerably simplifying the sample preparation procedure. It uses a fused-silica fibre that is coated on the outside with an appropriate stationary phase. The analytes in the sample are directly extracted to the fibre coating. The SPME technique can be routinely used in combination with gas chromatography, high-performance liquid chromatography and capillary electrophoresis and places no restriction on MS. SPME reduces the time necessary for sample preparation, decreases purchase and disposal costs of solvents and can improve detection limits. The SPME technique is ideally suited for MS applications, combining a simple and efficient sample preparation with versatile and sensitive detection. This review summarizes analytical characteristics and variants of the SPME technique and its applications in combination with MS.

Animals↗
PubMed2002

Comparison of microextraction procedures to determine pesticides in oranges by liquid chromatography-mass spectrometry.

A liquid chromatographic-mass spectrometric method has been developed for the determination of bitertanol, carbendazim, fenthion, flusilazole, hexythiazox, imidacloprid, methidathion, methiocarb, pyriproxyfen and trichlorfon. Two procedures, based on stir bar sorptive extraction (SBSE) and matrix solid-phase dispersion (MSPD), have been evaluated for the extraction of these compounds in oranges. Their respective advantages and disadvantages are also discussed. The recoveries obtained by MSPD ranged from 47 to 96% and the relative standard deviations (RSDs) ranged from 1 to 15%, whereas with the SBSE method the recoveries were between 8 and 84% and the RSDs between 4 and 16%. Although, the limits of quantitation of most compounds are much better (0.001-0.05 mg kg(-1)) by SBSE, it is not suitable to determine some polar pesticides as carbendazim, imidacloprid and trichlorfon. Results obtained by both methods were compared, in terms of sensitivity and selectivity, with a classical ethyl acetate extraction method, and the three methods were applied to analyze real samples. As MSPD is easier to perform, faster than the organic solvent extraction, and shows equal accuracy and resolution, its application for analyzing pesticides in oranges is recommended.

Chromatography, Liquid↗
PubMed1999

Comparative studies of the leachate of an industrial landfill by gas chromatography-mass spectrometry, liquid chromatography-nuclear magnetic resonance and liquid chromatography-mass spectrometry.

Nowadays, the need to have a realistic characterization of industrial effluents in the environment has become more and more recognized. A palette of different analytical methods both for sample extraction and instrumental analysis are available today, some older, others introduced more recently. The aim of this research is to compare a number of these techniques. To do this we studied a real leachate from an industrial landfill and carried out chemical analyses for organic pollutants, using different extraction methods based on solid-phase extraction and solid-phase microextraction and different instrumental techniques such as GC-MS, LC-MS, NMR and LC-NMR. Results show the performances of the different techniques, which are complementary.

Chromatography, Liquid↗
PubMed2004

Capillary liquid chromatographic determination of cellular flavins.

A capillary LC system was set up and optimized, in which a UV absorbance detector was used and a monolithic silica-ODS column as the separation column. Two on-line concentration techniques, namely, gradient elution mode and in-tube solid-phase ion-pair microextraction (SPIPME), were combined with the capillary LC system, which proved to be beneficial to enhance the concentration sensitivity by enabling the injection of large volumes of samples. The limits of detection at ppb levels for the flavins [riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)] were achieved using the two techniques. For in-tube SPIPME, a monolithic silica-ODS column was employed as the extraction column, on which FAD and FMN were retained b y interaction with an ion-pair reagent, tetrabutylammonium phosphate, resulting in greater than 110-fold enhancement in their concentration sensitivities relative to conventional injection method. The reproducibility and linearity of the two methods were investigated. The two methods were applied to analyze trace amounts of flavins in bacterial Escherichia coli cell extracts and recombinant flavoenzymes.

Chromatography, Liquid↗
PubMedDate not supplied

Concentration of fatty acid ethyl esters in hair of alcoholics: comparison to other biological state markers and self reported-ethanol intake.

AIMS: In a variety of clinical and forensic situations long term use of alcohol must be monitored. In this project we explore the utility of fatty acid ethyl esters (FAEE) in this regard. Additionally, we propose a cut-off value of FAEE to distinguish teetotallers/moderate/social drinkers from alcoholics or individuals drinking at harmful levels. PATIENTS AND METHODS: FAEE levels from 18 alcohol-dependent patients in detoxification were contrasted with those of 10 social drinkers and 10 teetotallers. FAEE in hair were determined, using headspace solid phase microextraction and gas chromatography mass spectrometry. C(FAEE), as sum of the concentrations of four esters, was compared to a major FAEE, ethyl palmitate. PEth was measured in heparinized whole blood with a high pressure liquid chromatography (HPLC) method. Drinking validation criteria include self reports, phosphatidyl ethanol (PEth) in whole blood as well as the traditional markers of heavy drinking, gamma glutamyl transpeptidase (GGT), mean corpuscular volume (MCV) and carbohydrate deficient transferrin (CDT). RESULTS: Receiver-operating characteristic (ROC) curve analysis for C(FAEE), indicated a sensitivity of 100% and a specificity of 90% for a cut-off of 0.29 ng/mg. By using a cut-off of 0.4 ng/mg, C(FAEE) identified 94.4% correctly. C(FAEE) and ethyl palmitate were significantly associated (r = 0.945; P < 0.001) as were C(FAEE) and PEth (r = 0.527; P = 0.025). No significant correlation was found between C(FAEE) and total grams of ethanol consumed last month, blood-alcohol concentration at admission to the hospital, CDT, MCV, or GGT. Among the serum and blood markers, %CDT identified 47.1%, MCV 38.8% and GGT 72.2% of patients with chronic intake of higher amounts of ethanol correctly, whereas PEth achieved 100% accuracy. CONCLUSIONS: The data suggest that C(FAEE) is a potentially valuable marker of chronic intake of high quantities of ethanol. Furthermore, the results indicate that a reasonable and provisional FAEE cut-off to distinguish between social/moderate and heavy drinking/alcoholism in hair is 0.4 ng/mg.

Adult↗
PubMed1998

Determination of carbonyl compounds in water by derivatization-solid-phase microextraction and gas chromatographic analysis.

The solid-phase microextraction (SPME) technique was evaluated for the determination of 23 carbonyl compounds in water. The carbonyl compounds in water were derivatized with omicron-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride (PFBHA), extracted with SPME from liquid or headspace and analyzed by GC with electron capture detection (GC-ECD). The effects of agitation techniques and the addition of salt (NaCl) on extraction, the absorption-time and absorption-concentration profiles were examined. The precision of the SPME technique for the determination of carbonyl compounds was evaluated with spiked bidistilled water, ozonated drinking water, and rain water. The relative standard deviations obtained from different spiked water matrix were similar, and in the range of 5.7-21.1%. The precision can be further improved by using an internal standard. With 4 ml of water sample, the limits of detection for most of the tested carbonyl compounds using liquid or headspace SPME-GC-ECD were similar and in the range of 0.006-0.2 micrograms/l, except for glyoxal and methylglyoxal, which showed low sensitivity when using headspace SPME. In the analysis of an ozonated drinking water sample, the SPME techniques gave comparable results to those of the conventional liquid-liquid extraction method.

Absorption↗
PubMed2006

Analytical discrimination of poisonous and nonpoisonous chemotypes of giant fennel (Ferula communis L.) through their biologically active and volatile fractions.

Giant fennel (Ferula communis L.) from Sardinia is characterized by two chemotypes with different biological activities. One chemotype is poisonous, due to prenylcoumarins, and responsible for ferulosis, which mainly affects sheep and goats, cattle, and horses; the other chemotype is nonpoisonous and contains daucane esters. The two chemotypes cannot be distinguished botanically. High-performance liquid chromatography-diode array-ultraviolet detection-mass spectrometry (HPLC-DAD-UV-MS) analysis of the composition of the fractions containing the biologically active metabolites and of the volatile fractions, by gas chromatography-mass spectrometry (GC-MS), of both essential oil and headspace sampled by headspace solid-phase microextraction (HS-SPME) are here shown to be effective in discriminating the poisonous and nonpoisonous chemotypes. HS-SPME with CAR/PDMS/DVB in combination with GC-MS has also been found to be a successful, fully automated one-step method for rapid and unequivocal discrimination of the two chemotypes, using aristolene and allohedycaryol as markers of the poisonous and nonpoisonous chemotypes, respectively.

Chromatography, High Pressure Liquid↗
PubMed2002

Determination of oxadiazon residues by headspace solid-phase microextraction and gas chromatography-mass spectrometry.

A method for the determination of trace amounts of the herbicide oxadiazon was developed using headspace solid-phase microextraction (HS-SPME), gas chromatography-mass spectrometry (GC-MS) and selected ion monitoring. It was applied to determine oxadiazon in ground water, agricultural soil, must, wine and human urine samples. To determine oxadiazon in liquid samples, a response surface methodology generated with a Doehlert design was applied to optimize the HS-SPME conditions using a 100 microm polydimethylsiloxane fibre. For the analysis of soil samples, they were mixed with water and the SPME fibre suspended in the headspace above the slurry. Ground water, human urine and must show linear concentration range of application of 0.5-50 ng ml(-1)' with detection limits < or =0.02 ng ml(-1). HS-SPME-GC-MS analysis yielded good reproducibility (RSD values between 6.5 and 13.5%). The method validation was completed with spiked matrix samples. The developed analytical procedure is solvent free, cost effective and fast.

Gas Chromatography-Mass Spectrometry↗
PubMed2006

SPME in environmental analysis: biotransformation pathways.

Solid-phase microextraction (SPME) is an organic solvent-free sample preparation tool suitable for direct adsorption of analytes from the headspace or the aqueous phase of a matrix followed by desorption into a gas chromatograph (GC) or high-performance liquid chromatograph (HPLC) for subsequent analysis. The SPME technique is designed to accommodate the use of fibers coated with different polymers suitable for the extraction of chemicals with varied hydrophobic and polar properties. Also, the technique can minimize interference from other artefacts associated with complex samples, such as those encountered in biological matrices or reaction mixtures. The preceding characteristics of SPME make the technique suitable for real-time measurements of intermediate reaction products and, thus, able to provide insight into the fate of target chemicals and their degradation pathways. In the present article, the current state of knowledge on the use of SPME-GC and SPME-HPLC in the determination of frequently encountered environmental chemicals and their (bio)transformation pathways are critically reviewed. Future opportunities of SPME in real time in situ process monitoring such as the use of agricultural feed stocks to bio-based industrial products termed henceforth "process analytical chemistry" are also discussed.

Biotransformation↗
PubMed2004

New trend in sample preparation: on-line microextraction in packed syringe for liquid and gas chromatography applications. I. Determination of local anaesthetics in human plasma samples using gas chromatography-mass spectrometry.

A new technique for sample preparation on-line with LC and GC-MS assays was developed. Microextraction in a packed syringe (MEPS) is a new miniaturised, solid-phase extraction technique that can be connected on-line to GC or LC without any modifications. In MEPS approximately 1mg of the solid packing material is inserted into a syringe (100-250 microl) as a plug. Sample preparation takes place on the packed bed. The bed can be coated to provide selective and suitable sampling conditions. The new method is very promising. It is very easy to use, fully automated, of low cost and rapid in comparison with previously used methods. This paper presents the development and validation of a method for microextraction in packed syringe MEPS on-line with GC-MS. Local anaesthetics in plasma samples were used as model substances. The method was validated and the standard curves were evaluated by the means of quadratic regression and weighted by inverse of the concentration: 1/x for the calibration range 5-2000 nM. The applied polymer could be used more than 100 times before the syringe was discarded. The extraction recovery was between 60 and 90%. The results showed close correlation coefficients (R>0.99) for all analytes in the calibration range studied. The accuracy of MEPS-GC-MS was between 99 and 115% and the inter-day precision (n=3 days), expressed as the relative standard deviation (R.S.D.%), was 3-10%.

Anesthetics, Local↗
PubMed2005

Focused microwave-assisted extraction combined with solid-phase microextraction and gas chromatography-mass spectrometry for the selective analysis of cocaine from coca leaves.

An effective combination of focused microwave-assisted extraction (FMAE) with solid-phase microextraction (SPME) prior to gas chromatography (GC) is described for the selective extraction and quantitative analysis of cocaine from coca leaves (Erythroxylum coca). This approach required switching from an organic extraction solvent to an aqueous medium more compatible with SPME liquid sampling. SPME was performed in the direct immersion mode with a universal 100 microm polydimethylsiloxane (PDMS) coated fibre. Parameters influencing this extraction step, such as solution pH, sampling time and temperature are discussed. Furthermore, the overall extraction process takes into account the stability of cocaine in alkaline aqueous solutions at different temperatures. Cocaine degradation rate was determined by capillary electrophoresis using the short end injection procedure. In the selected extraction conditions, less than 5% of cocaine was degraded after 60 min. From a qualitative point of view, a significant gain in selectivity was obtained with the incorporation of SPME in the extraction procedure. As a consequence of SPME clean-up, shorter columns could be used and analysis time was reduced to 6 min compared to 35 min with conventional GC. Quantitative results led to a cocaine content of 0.70 +/- 0.04% in dry leaves (RSD <5%) which agreed with previous investigations.

Chemical Fractionation↗
PubMed2006

Fast in vivo microextraction: a new tool for clinical analysis.

BACKGROUND: We sought to develop a technique with the potential to partly replace current methods of analysis based on blood draws. To achieve this goal, we developed an in vivo microextraction technique that is faster than conventional methods, interferes minimally with the investigated system, minimizes errors associated with sample preparation, and limits exposure to hazardous biological samples. METHODS: Solid-phase microextraction devices based on hydrophilic polypyrrole and polyethylene glycol coatings were used for direct extraction of drugs from the flowing blood of beagle dogs, over a period of 8 h. The drugs extracted on the probes were subsequently quantified by liquid chromatography coupled to tandem mass spectrometry. Two calibration strategies--external and standard on the fiber--were used to correlate the amount extracted with the in vivo concentration. RESULTS: Diazepam and its metabolites were successfully monitored over the course of a pharmacokinetic study, repeated 3 times on 3 beagles. The fast microextraction technique was validated by comparison with conventional plasma analysis, and a correlation factor of 0.99 was obtained. In addition to total concentrations, the method was useful for determining free drug concentrations. CONCLUSIONS: The proposed technique has several advantages and is suitable for fast clinical analyses. This approach could be used not only for drugs, but for any other endogenous or exogenous compounds.

Animals↗
PubMed2004

Magnetic field enhanced microextraction rate of europium(III) with 2-thenoyltrifluoroacetone and oxalate at dodecane-water interface.

A microscopic system for the observation of reactions at a liquid-liquid interface was established, to which strong magnetic fields (0-0.4 T) could be applied with permanent magnets. In situ observation for the interfacial extraction of fluorescent and paramagnetic Eu(III) ion with 2-thenoyltrifluoroacetone (Htta) in dodecane was carried out. In the presence of oxalate (ox2-), micro-aggregates of Eu(III)-tta-ox complexes were generated in the aqueous phase before its extraction. When the micro-aggregates diffused to the dodecane-water interface, Eu(tta)3 was extracted with excess Htta in the dodecane phase. The microextraction process of the aggregates was observed as random flashes of Eu(tta)3 fluorescence at the dodecane-water interface. The single flash contained about 10(-16)-10(-14) mol of Eu(III). An application of magnetic fields made the flash frequency increase, which corresponded to an enhancement of interfacial Eu(III) extraction rate. The enhancement effect was attributable to the magnetophoresis of the paramagnetic microaggregates to the dodecane-water interface.

Journal Article↗
PubMed2006

Trace element determination by combining solid-phase microextraction hyphenated to elemental and molecular detection techniques.

The state of the art of analytical procedures based on solid-phase microextraction (SPME) and its applications to tin, mercury, arsenic, antimony, chromium, selenium, and lead determination in abiotic and biotic matrixes are critically reviewed from 1994 to present. First, sample pretreatment prior to SPME is evaluated, including a description of the most usual leaching procedures for sediment, soil, and biological samples. Because most organometallic species lack volatility, a derivatization step is mandatory prior to gas chromatographic (GC) determination, except for the volatile organometallics that can be directly extracted from the sample headspace or liquid phase by SPME. The most common derivatization procedures used in alkylation and hydridization reactions used for mercury, lead, and tin, as well as other procedures for the determination of total chromium and arsenic [i.e., trifluoroacetylacetonates for chromium (III) and thioglycol methylate for organic arsenic species] are reviewed. Critical variables usually evaluated along with the method development to improve the sensitivity of the extraction methods based on SPME, such as sampling size, stirring procedures, sampling temperature and pressure, polymer coating, and thermal desorption are reviewed. In addition, figures of merit of the different detection systems used in SPME combined with GC are evaluated. The validation of the reported analytical procedures with reference materials are also discussed in terms of precision and accuracy. Finally, future developments in the application of SPME to speciation are highlighted. Moreover, the capability of SPME automation for the derivatization-extraction procedures are also presented.

Journal Article↗
PubMed2005

Molecular characterisation of birch bark tar by headspace solid-phase microextraction gas chromatography-mass spectrometry: a new way for identifying archaeological glues.

To develop an analytical methodology, as non-destructive as possible, suitable for the identification of natural substances from archaeological origin, we studied the potentiality of solid-phase microextraction (SPME) for analysing birch bark tar, an adhesive commonly used during ancient times. First of all, birch bark tars were produced by a controlled heating of birch bark. The two kinds of samples obtained using different processes of fabrication, one at liquid state, the second one at solid state, were then analysed by headspace HS-SPME-GC-MS. Different conditions of sample treatment were tested (two different fibre coatings, various times and temperatures of extraction) in order to suggest optimal conditions for the analysis of birch bark tar. Both samples were shown to be rich in volatile organic components. Two main groups of constituents, namely phenolic compounds issued from lignin or tannin known to be present in bark and sesquiterpenoid hydrocarbons, secondary metabolites largely distributed in the plant kingdom, were detected for the first time in birch bark tar. HS-SPME-GC-MS appears thus to be a very efficient method for investigating the volatiles emitted by plant tars and could be further used for the study of birch bark tar samples issued from archaeological context.

Adhesives↗
PubMed1998

Comparison of simplified methods for pesticide residue analysis. Use of large-volume injection in capillary gas chromatography.

The combination of manual and automated extraction procedures using low sample volumes (5-50 ml) with large-volume oncolumn injection (LVI) (200 microliters) in capillary gas chromatography with flame photometric detection (GC-FPD) has allowed the determination of 16 organophosphorus pesticides in clean water samples at the low ng l-1 level with an important simplification in the sample preparation step. A simple and fast offline liquid-liquid microextraction procedure (2-5 ml water/l ml methyl tert.-butyl ether) has been applied to spiked groundwater samples (containing 0.5 ng of each pesticide) with good recoveries (over 80%) and precision (better than 10%), giving detection limits between 5 and 100 ng l-1 using 200 microliters injections in the GC-FPD system. The application of an inline automated liquid-liquid microextraction-LVI-GC procedure (2 ml water/2 ml methyl tert.-butyl ether: injection of 200 microliters in GC-FPD) using the autosampler ASPEC XL led to lower recoveries (> 50%) as a result of the low efficiency for mixing organic and aqueous phases, although with very satisfactory coefficients of variation (lower than 7%) and detection limits between 20 and 200 ng l-1. Manual and automated solid-phase extraction procedures using the well known C18 cartridges and the new Oasis HLB have been applied to groundwater samples (5-50 ml) spiked with 1 ng of each pesticide. Results obtained for both the manual and the automated procedures were satisfactory (recoveries over 80%) and the limits of detection for 50 ml sample volume ranged from 1 to 6 ng l-1.

Autoanalysis↗