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PubMedDate not supplied

Use of solid-phase microextraction (SPME) for the determination of methadone and its main metabolite, EDDP, in plasma by gas chromatography-mass spectrometry.

A simple, rapid method for the determination of methadone and its metabolite 2-ethylene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) in plasma using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry is proposed. A 100-microm polydimethylsiloxane film fiber was exposed by immersion for 30 min in a diluted plasma solution (1:4 with buffer pH 9) containing both compounds and an internal standard (proadifen). Calibration curves were linear over the concentration range 50-2000 ng/mL. The analysis time was 45 min per sample. The determination of methadone and EDDP was subject to no interference. The performance of SPME was compared with that of liquid-liquid extraction, obtaining lower limits of detection for EDDP. The method using the two extraction procedures was applied to 10 plasma samples from methadone-treated patients.

Calibration↗
PubMed2000

Sample preparation for the analysis of flavors and off-flavors in foods.

Off-flavors in foods may originate from environmental pollutants, the growth of microorganisms, oxidation of lipids, or endogenous enzymatic decomposition in the foods. The chromatographic analysis of flavors and off-flavors in foods usually requires that the samples first be processed to remove as many interfering compounds as possible. For analysis of foods by gas chromatography (GC), sample preparation may include mincing, homogenation, centrifugation, distillation, simple solvent extraction, supercritical fluid extraction, pressurized-fluid extraction, microwave-assisted extraction, Soxhlet extraction, or methylation. For high-performance liquid chromatography of amines in fish, cheese, sausage and olive oil or aldehydes in fruit juice, sample preparation may include solvent extraction and derivatization. Headspace GC analysis of orange juice, fish, dehydrated potatoes, and milk requires almost no sample preparation. Purge-and-trap GC analysis of dairy products, seafoods, and garlic may require heating, microwave-mediated distillation, purging the sample with inert gases and trapping the analytes with Tenax or C18, thermal desorption, cryofocusing, or elution with ethyl acetate. Solid-phase microextraction GC analysis of spices, milk and fish can involve microwave-mediated distillation, and usually requires adsorption on poly(dimethyl)siloxane or electrodeposition on fibers followed by thermal desorption. For short-path thermal desorption GC analysis of spices, herbs, coffee, peanuts, candy, mushrooms, beverages, olive oil, honey, and milk, samples are placed in a glass-lined stainless steel thermal desorption tube, which is purged with helium and then heated gradually to desorb the volatiles for analysis. Few of the methods that are available for analysis of food flavors and off-flavors can be described simultaneously as cheap, easy and good.

Flavoring Agents↗
PubMed2000

Optimisation of alachlor solid-phase microextraction from water samples using experimental design.

We have tested screening and response surface experimental designs to optimise the solid-phase microextraction (SPME) of the widely used herbicide alachlor. Extraction time and sample volume were the only statistically significant factors from those studied. In the final optimised conditions the procedure was applied to the SPME-HPLC analysis of alachlor in spiked water samples with excellent figures of merit.

Acetamides↗
PubMed2002

[New technologies of solid-phase microextraction].

Solid-phase microextraction (SPME) is a technology with functions of sampling, extraction and concentration based on adsorption/absorption-desorption equilibrium between coating and sample. The recent development of SPME is reviewed. Studies on the in-tube-SPME technology, novel extraction probes and its coupling with other analytical technologies are summarized.

Adsorption↗
PubMed2003

Analysis of volatiles of malt whisky by solid-phase microextraction and stir bar sorptive extraction.

Blended Scotch whisky was analysed by solid-phase microextraction (SPME) and stir bar sorptive extraction (SBSE) to study the composition of the volatiles. For SPME analysis, three different fibres were compared, poly(dimethylsiloxane) (PDMS) (100 microm). poly(acrylate) (PA) (85 microm) and divinylbenzene-Carboxen on poly(dimethylsiloxane) (DVB-CAR-(PDMS) (50/30 microm). It was found that the PDMS and DVB-CAR-PDMS fibres showed a higher enrichment capacity than PA as well as a better reproducibility. The influence of sampling time, temperature and salt addition on the enrichment of volatiles as well as the difference between liquid and headspace SPME were studied. An optimum SPME method was developed. Finally a more recent sample preparation technique, namely SBSE was evaluated to extract whisky volatiles.

Alcoholic Beverages↗
PubMed2003

Metabolite identification in drug discovery.

Recent developments in the technologies and approaches to identify metabolites in a drug discovery environment are reviewed. Samples may be generated using either in vitro systems--typically, but not exclusively, liver subcellular fractions, such as microsomes, or whole cells, such as hepatocytes. Alternatively, metabolites are generated in vivo using excreta obtained following dosing in preclinical species. Recombinant drug metabolizing enzymes or microorganisms may offer alternate vectors. New techniques, such as the use of solid-phase microextraction, have found application in the isolation of metabolites from biological matrices. However, this is still dominated by the use of preparative chromatography, which has advanced through the use of mass-directed detection. Detection and structural elucidation by mass spectrometry have improved markedly with increases in sensitivity, allowing lower abundance metabolites to be detected, and increases in selectivity, with the use of high-resolution time-of-flight and quadrupole-time-of-flight instruments. Finally, higher field strength magnets coupled with novel probe designs and increased use of liquid chromatographic hyphenation techniques continue to drive the capabilities of nuclear magnetic resonance spectroscopy as the definitive structural elucidation tool.

Animals↗
PubMed2003

Determination of antifouling compounds in marine sediments by solid-phase microextraction coupled to gas chromatography-mass spectrometry.

Solid-phase microextraction (SPME) coupled to gas chromatography-mass spectrometry was applied to determine the antifouling biocides chlorothalonil, dichlofluanid, sea nine 211 and irgarol 1051 in marine sediments. Two experimental approaches were selected before the submission of the aqueous extracts to SPME prior to GC determination. The extraction of the biocides from the sediment samples was conducted using (a) water (containing 5%, v/v, acetone) and (b) acetone which was then diluted with water to give a 5% (v/v) content. The recommended procedures were found to be applicable for quantitative determination of the selected antifouling compounds in sediments with R.S.D.s below 17% and limits of detection ranging from 0.5 to 25 ng/g. The acetone/SPME procedure showed lower detection limits (0.5 to 6 ng/g) and R.S.D. values (< 11%) as well as better recoveries (73 to 92%), proving that it could be successfully performed for the determination of antifouling compounds in sediment analysis, even in samples with high organic matter content. Both optimized water/SPME and acetone/SPME procedures were applied to the analysis of antifouling compounds in marine sediments and compared with the conventional liquid-liquid extraction with subsequent clean up by solid-phase extraction.

Aniline Compounds↗
PubMed1999

Determination of carphedon in human urine by solid-phase microextraction using capillary gas chromatography with nitrogen-phosphorus detection.

Carphedon is a phenyl derivative of nootropil and is effective in increasing physical endurance and cold resistance, and is used for amnesia treatment. Carphedon was extracted from human urine samples by solid-phase microextraction with a 65 microns carbowax-divinylbenzene-coated fiber. This analysis was performed by using capillary gas chromatography with nitrogen-phosphorus detection and optimized at pH 9.6, 30% NaCl, immersion time 10 min and desorption in the GC injector at 250 degrees C for 3 min. The regression equation for carphedon showed good linearity in the range from 0.1 to 10 micrograms ml-1 for human urine samples. The limit of detection was 0.01 microgram ml-1. The developed method is more sensitive and simpler in sample preparation than liquid-liquid extraction and can be applied to doping analysis for stimulants.

Central Nervous System Stimulants↗
PubMed2000

Determination of organophosphorus insecticides in natural waters using SPE-disks and SPME followed by GC/FTD and GC/MS.

Two methods for the analysis of ten organophosphorus insecticides in natural waters using solid phase extraction disks containing C18 and SDB and solid phase microextraction fibers containing polyacrylate (PA) are developed. Bromophos ethyl, bromophos methyl, dichlofenthion, ethion, fenamiphos, fenitrothion, fenthion, malathion, parathion ethyl and parathion methyl were determined by GC/MS and GC/FTD. The SPE-disks require only 1000 mL of sample and provide a method limit of detection in the range of 0.01-0.07 microgram/L and recovery rates from 60.7 to 104.1%. The solid phase microextraction (SPME) technique requires 2-5 mL of water sample and provides a method limit of detection in the range of 0.01 to 0.05 microgram/L for all detectors and the recoveries compared to distilled water ranged from 86.2 to 119.7%. The proposed methods were applied to the trace level screening determination of insecticides in river water samples originating from different Greek regions.

Calibration↗
PubMed2001

Application of low-temperature glassy carbon films in solid-phase microextraction.

Low-temperature glassy carbon (LTGC) films were investigated as a sorbent coating for solid-phase microextraction because of its uniquely selective adsorptive characteristics. The selectivity of these coatings is primarily controlled by shape characteristics of the solute molecule and the final processing temperature used to form the LTGC, demonstrating unique adsorptive characteristics compared to commercial phases. The LTGC films were prepared by first coating porous silica particles with a diethylnyl oligomer precursor and then heat curing at temperatures between 300 and 1000 degrees C to form the LTGC. Then, using a sol-gel process, the LTGC-coated silica particles were immobilized onto stainless steel fibers and subsequently used for headspace and liquid extractions followed by GC-FID analysis. The selectivity of the LTGC is demonstrated by the extraction of a variety of aromatic hydrocarbons as well as the taste and odor contaminants geosmin, 2-methylisoborneol, and 2,4,6-trichloroanisole commonly found in water supplies. The data show that the LTGC coating has the highest affinity for molecules with the greatest cross-sectional surface area and polarizability and that this selective mechanism increases as a function of LTGC processing temperature.

Journal Article↗
PubMed2002

Improvement of measurement precision of SPME-GC/MS determination of tributyltin using isotope dilution calibration.

A unique approach was developed to improve the precision of quantification of tributyltin (TBT) in sedimentsby solid phase microextraction (SPME) using isotope dilution GC/MS. The precision of the analytical technique was initially evaluated using standard calibration solutions. In selective ion monitoring (SIM) mode, the relative standard deviation (RSD) obtained for TBT based on peak area response was 18% (n = 11). When an internal standard, tripropyltin (TPrT), was used, the RSD decreased to 12%. A significant improvement in the precision using SPME was noted when a 117Sn-enriched TBT spike was employed; the RSD decreased 4-fold to 3%. Detection limits of 0.2 and 20 ng(Sn) L(-1) were achieved with SPME sampling and liquid-liquid extraction, respectively. Six analyses were performed for determination of TBT in PACS-2 sediment Certified Reference Material using both standard additions and isotope dilution procedures. For the latter, a 117Sn-enriched TBT spike was used. A concentration of 0.88 +/- 0.03 microg g(-1) (RSD 3.4%) obtained using standard additions was in good agreement with the certified value of 0.98 +/- 0.13 microg g(-1) as tin. Concentrations found using isotope dilution were 0.895 +/- 0.015 microg g(-1) (RSD 1.73%) as tin and 0.874 +/- 0.014 microg g(-1) (RSD 1.66%) as tin using a liquid-liquid extraction and SPME sampling, respectively. A 2-fold improvement in the precision of TBT concentration measurement using isotope dilution was clearly achieved, demonstrating its superiority in providing more accurate and precise results as compared to the method of standard additions. The isotope dilution technique eliminated the problem of poor reproducibility, which typically plagues SPME.

Calibration↗
PubMed2000

Simultaneous determination of cyanogen chloride and cyanogen bromide in treated water at sub-microg/L levels by a new solid-phase microextraction-gas chromatographic-electron-capture detection method.

A headspace solid-phase microextraction (HS-SPME) procedure has been developed and applied for the determination of cyanogen halides in treated water samples at microg/L concentrations. Several SPME coatings were tested, the divinylbenzene-Carboxen-polydimethylsiloxane fiber being the most appropriate coating. GC-electron-capture detection was used for separation and quantitation. Experimental parameters such as sample volume, addition of a salt, extraction time and desorption conditions were studied. The optimized method has an acceptable linearity, good precision, with RSD values <10% for both compounds, and it is sufficiently sensitive to detect ng/L levels. HS-SPME was compared with liquid-liquid microextraction (US Environmental Protection Agency Method 551.1) for the analysis of spiked ultrapure and granular activated carbon filtered water samples. There was good agreement between the results from both methods. Finally, the optimized procedure was applied to determine both compounds at the Barcelona water treatment plant (N.E. Spain). Cyanogen chloride in treated water was <1.0 microg/L and cyanogen bromide ranged from 3.2 to 6.4 microg/L.

Adsorption↗
PubMed2000

Use of solid-phase microextraction (SPME) for the determination of methadone and EDDP in human hair by GC-MS.

Solid-phase microextraction (SPME) is a new extraction technique with many advantages: small sample volume, simplicity, quickness and solvent-free. It is mainly applied to environmental analysis, but is also useful for the extraction of drugs from biological samples. In this paper the use of SPME is proposed for the determination of methadone and its main metabolite EDDP in hair by GC-MS. The hair samples were washed, cut into 1-mm segments, and incubated with Pronase E for 12 h. A 100-micron polydimethylsiloxane (PDMS) film fibre was submerged for 30 min in a diluted solution of the hydrolysis liquid (1:4 with borax buffer) containing methadone-d3 and EDDP-d3 as internal standards. Once the microextraction was concluded the fibre was directly inserted into the CG injection port. Linearity was found for methadone and EDDP in the range studied, 1.0-50 ng/mg hair, with correlation coefficients higher than 0.99. Interassay relative standard deviation (R.S.D) was determined to be less than 13.30% for methadone and less than 8.94% for EDDP, at 3.0 and 30.0 ng/mg. Analytical recoveries were close to 100% for both compounds on spiked samples. The method was applied to the analysis of real hair samples from eight patients of a methadone maintenance programme. The concentration of methadone in hair ranged from 2.45 to 78.10 ng/mg, and for EDDP from 0.98 to 7.76 ng/mg of hair.

Calibration↗
PubMed2000

Biotransformation of geraniol, nerol and citral by sporulated surface cultures of Aspergillus niger and Penicillium sp.

The biotransformation of geraniol, nerol and citral by Aspergillus niger was studied. A comparison was made between submerged liquid, sporulated surface cultures and spore suspensions. This bioconversion was also carried out with surface cultures of Penicillium sp. The main bioconversion products obtained from geraniol and nerol by liquid cultures of A. niger were linalool and alpha-terpineol. Linalool, alpha-terpineol and limonene were the main products obtained from nerol and citral by sporulated surface cultures, whereas geraniol was converted predominantly to linalool, also resulting in higher yields. Bioconversion of nerol with Penicillium chrysogenum yielded mainly alpha-terpineol and some unidentified compounds. With P. rugulosum the major bioconversion product from nerol and citral was linalool. The bioconversion of nerol to alpha-terpineol and linalool by spore suspensions of A. niger was also investigated. Finally the biotransformation with sporulated surface cultures was also monitored by solid phase microextraction (SPME). It was found that SPME is a very fast and efficient screening technique for biotransformation experiments.

Acyclic Monoterpenes↗
PubMed2003

Determination of limonene oxidation products using SPME and GC-MS.

Limonene is a common component found in consumer goods ranging from beverages to cleaning compounds. Limonene oxidation products, however, have a less desirable flavor and fragrance. Early detection of limonene oxide formation would aid quality control. A method is developed to determine the concentration of limonene oxide in essential oils and beverages using solid-phase microextraction (SPME). A headspace sampling technique is used to reduce or eliminate the presence of less volatile components. Several different SPME fibers are tested, varying in polymer thickness, polymer cross-linking and bonding, and polarity of the polymer. For each fiber tested, the sampling time is optimized for reproducible results. The 7-microm-thick bonded poly(dimethylsiloxane) fiber provides the best results. External standards are used for quantitation.

Chromatography, Liquid↗
PubMed2001

Determination of polychlorinated biphenyls in milk samples by saponification-solid-phase microextraction.

A saponification-HSSPME procedure has been developed for the extraction of PCBs from milk samples. Saponification of the samples improves the PCB extraction efficiency and allows attaining lower background. A mixed-level fractional design has been used to optimize the sample preparation process. Five variables have been considered: extraction time, agitation, kind of microextraction fiber, concentration, and volume of NaOH aqueous solution. Also the kinetic of the process has been studied with the two fibers (100-microm PDMS and 65-microm PDMS-DVB) included in this study. Analyses were performed on a gas chromatograph equipped with an electron capture detector and a gas chromatograph coupled to a mass selective detector working in MS-MS mode. The proposed method is simple and rapid, and yields high sensitivity, with detection limits below 1 ng/mL, good linearity, and reproducibility. The method has been applied to liquid milk samples with different fat content covering the whole commercial range, and it has been validated with powdered milk certified reference material.

Animals↗
PubMed1997

Determination of urinary acylcarnitines by ESI-MS coupled with solid-phase microextraction (SPME).

The determination of selected short-, medium- and long-chain acylcarnitines by electrospray ionization mass spectrometry (ESI-MS) is discussed. The differences in fragmentation behaviour and ionization efficiency are described in dependence on collision induced dissociation (CID) conditions and mixture composition. A new method combination, solid-phase microextraction (SPME)-ESI-MS, is introduced to characterize acylcarnitines in body fluids. This method utilizes SPME for pre-concentration of acylcarnitines from complex biological samples and ESI-MS for a selective and sensitive detection. The method is presented by standard experiments determining of acylcarnitines in aqueous solutions and urine samples from patients with secondary carnitine deficiency syndromes or related disorders.

Calibration↗
PubMed2001

Solid-phase microextraction of hop volatiles. Potential use for determination and verification of hop varieties.

The composition of hop essential oil is an important tool for evaluation of hop quality. As each hop variety has a typical essential oil pattern (fingerprint), hop oil analyses can be used to distinguish between hop varieties. The headspace solid-phase microextraction (SPME) method as described in this contribution is a simple sample preparation technique and represents an alternative procedure for essential oil fingerprint determination. Different SPME parameters (extraction temperature, extraction time and sample mass) were studied and the results were compared with those obtained by the routine distillation method. It is shown that SPME results can be used for determination and verification of varieties grown in Slovenia by means of principal components analysis.

Chromatography, Liquid↗