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PubMed2000

Headspace solid-phase microextraction procedures for gas chromatographic analysis of biological fluids and materials.

Solid-phase microextraction (SPME) is a new solventless sample preparation technique that is finding wide usage. This review provides updated information on headspace SPME with gas chromatographic separation for the extraction and measurement of volatile and semivolatile analytes in biological fluids and materials. Firstly the background to the technique is given in terms of apparatus, fibres used, extraction conditions and derivatisation procedures. Then the different matrices, urine, blood, faeces, breast milk, hair, breath and saliva are considered separately. For each, methods appropriate for the analysis of drugs and metabolites, solvents and chemicals, anaesthetics, pesticides, organometallics and endogenous compounds are reviewed and the main experimental conditions outlined with specific examples. Then finally, the future potential of SPME for the analysis of biological samples in terms of the development of new devices and fibre chemistries and its coupling with high-performance liquid chromatography is discussed.

Body Fluids↗
PubMed2004

Relationship between procyanidin and flavor contents of cocoa liquors from different origins.

The flavor of eight cocoa liquors of different origins (Africa, America, and Asia) and different varieties (Fine grades: criollo, trinitario, and nacional. Bulk-basic grade: forastero.) was analyzed by headspace solid-phase microextraction mass spectrometry (HS-SPME-MS). Their procyanidin contents were quantified by HPLC-UV (280 nm). Fine varieties with short fermentation processes proved to contain more procyanidins, while criollo from New Guinea and forastero beans showed the highest aroma levels. The levels of cocoa aroma compounds formed during roasting are shown to vary directly with bean fermentation time and inversely with residual procyanidin content in cocoa liquor. Measurement of antioxidant activity in cocoa liquor proved to be a useful tool for assessing residual polyphenols.

Africa↗
PubMed2005

Development of a solid-phase microextraction method for direct determination of pentachlorophenol in paper and board samples: Comparison with conventional extraction method.

A solid-phase microextraction (SPME) method has been developed for the determination of pentachlorophenol (PCP) in paper and board samples. The analytical procedure involves direct extraction of PCP from paper and board samples and determination by gas chromatography with electron capture detection (GC-ECD). Two kinds of commercially available fibres; 100 microm polydimethylsiloxane (PDMS), apolar, and 85 microm polyacrylate (PA), quite polar, were evaluated to determine the extraction efficiency of pentachlorophenol. Parameters affecting the extraction process, such as temperature and time, were studied. Moreover, time of desorption and the effect of addition of salt were also investigated. The optimized procedure was applied to the analysis of pentachlorophenol (PCP) in five samples of virgin and recycled paper and board. The PCP content was determined by GC-ECD. To evaluate the effectiveness of the proposed method, it was compared with conventional extraction method with liquid-liquid extraction and derivatization. Detection limit of 0.015 microg/g for PCP in paper was achieved with a RSD of 14%.

Chemical Fractionation↗
PubMed2004

Solid-phase microextraction with on-fiber derivatization for the analysis of anti-inflammatory drugs in water samples.

A sensitive and solvent-free procedure for the determination of non-steroidal acidic anti-inflammatory drugs in water samples was optimized using solid-phase microextraction (SPME) followed by on-fiber silylation of the acidic compounds and gas chromatography-mass spectrometry (GC-MS) determination. Microextraction was carried out directly over the filtered water samples using a polyacrylate fiber. Derivatization was performed placing the SPME fiber, loaded with the extracted analytes, in the headspace of a vial containing 50 microl of N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA). Derivatives were desorbed for 3 min in the GC injector. Influence of several parameters in the efficiency of microextraction (volume of sample, time, pH, type of fiber coating, etc.) and derivatization steps (time, temperature and volume of MTBSTFA) was systematically investigated. In the optimal conditions an excellent linearity over three orders of magnitude and quantification limits at the ng/l level (from 12 to 40 ng/l) were achieved. The proposed method was applied to the determination of acidic compounds in sewage water and results compared to those obtained using solid-phase extraction (SPE) followed by the derivatization of the compounds in the organic extract of the solid-phase extraction cartridge.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Solid-phase microextraction (SPME) technique for measurement of generation of fresh cucumber flavor compounds.

Investigations were carried out to determine whether flavor compounds characteristic for fresh cucumbers could be rapidly determined using a solid-phase microextraction (SPME) dynamic headspace sampling method combined with gas chromatography and flame ionization detection. Cucumbers were sampled, during blending, for fresh cucumber flavor compounds (E,Z)-2,6-nonadienal and (E)-2-nonenal. The GC was such that the two target compounds were separated and baseline-resolved. Relative standard deviations for analysis of both (E,Z)-2,6-nonadienal and (E)-2-nonenal using this SPME sampling method were +/-10%. Utility of the analytical method was demonstrated by determining the effect of heat treatments on the ability of cucumbers to produce these flavor impact compounds.

Chromatography, Gas↗
PubMed2005

Depletion solid-phase microextraction for the evaluation of fiber-sample partition coefficients of pesticides.

A depletion solid-phase microextraction (SPME) method for the characterisation of SPME sorption for 13 pesticides selected as probe compounds is described. The sample is extracted and analysed multiple times by SPME-GC/MS. The observed depletion in peak areas is used for the calculation of extraction ratios that varied between 3 and 28% for a PDMS fiber with confidence intervals between 0.7 and 5.4%. Apparent fiber-sample partition coefficients can be calculated and extrapolated to equilibrium conditions if specific sorption kinetics are known. Under the chosen conditions, problems were encountered for more polar compounds (logK(ow)<3) due to inefficient extraction. The extracted amount was found to be the decisive parameter for depletion SPME and the extraction conditions therefore need to be adapted to the polarity of the analyte. The importance of the initial analyte concentration especially for mixed-mode fibers is demonstrated. Compared with conventional external calibration using liquid injection, depletion SPME eliminates uncertainties due to solvent effects during injection. Furthermore, it does neither require authentic reference compounds nor knowledge of the initial analyte concentration, and thus can even be used for unknowns.

Adsorption↗
PubMed2003

Nitrogen isotope analysis of ammonium in aqueous solutions using a perfluorosulfonated ionomer membrane for solid-phase microextraction.

The use of custom-made solid-phase microextraction (SPME) fibers coated with a perfluorosulfonated ionomer, Nafion, was investigated for nitrogen isotopic analysis of ammonium in aqueous solutions. Aqueous ammonium was converted to ammonia by addition of a base, followed by absorption from the headspace, desorption in the injection port of a gas chromatograph, and analysis by gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS). Fibers coated with a Nafion tubing were chosen due to a higher fiber-gas distribution constant and a higher Nafion thickness than fibers coated with Nafion solution, both leading to a higher amount of ammonia absorbed at equilibrium. The Nafion membrane-coated fiber absorbed approximately 20 times more than a commercial polydimethylsiloxane (PDMS) fiber. The isotopic fractionation between fiber and gas was 1.0117 +/- 0.0009 (standard deviation, SD, of all measurements) at an initial ammonia gas concentration of 21-210 microM. At 390 microM initial gas concentration it was slightly lower. When sampling from liquid samples, an ammonium concentration of 10 mM was needed to obtain a sufficient amount of ammonia absorbed. Modeling of the absorption at different temperatures showed that the absorption was approximately constant in the temperature range suitable for SPME experiments. Absorption at room temperature was therefore used for simplicity. A pilot study was conducted in which absorption was achieved from a single 9 microL droplet of sample. The preliminary results showed that delta(15)N analysis was possible for only 0.4-0.5 micromol of ammonium with a SD of 0.8 per thousand (n = 5).

Algorithms↗
PubMed2003

Headspace solid-phase microextraction in combination with gas chromatography-mass spectrometry for the rapid screening of organophosphorus insecticide residues in strawberries and cherries.

A headspace solid-phase microextraction (HS-SPME) method in combination with GC-MS was used for the extraction and quantification of diazinon, fenitrothion, fenthion, parathion ethyl, bromophos methyl, bromophos ethyl and ethion. The method was developed using a 100-microm poly(dimethylsiloxane) fiber. The obtained results showed higher responses of the insecticides after addition of aliquots of water and solvent to the fruit samples. Calibration curves that were constructed for the analytes spiked into strawberry and cherry samples followed linear relationships with good correlation coefficients (R2 > 0.986). Linearity range was between 50 and 500 microg/kg and the precision was found to be lower than 15% when applying the optimized HS-SPME procedure to fruit samples. Limits of detection in both strawberry and cherry samples using GC-MS (selected ion monitoring mode) were below 13 microg/kg. Moreover, the HS-SPME method was applied to the analysis of fruit samples and compared with liquid-liquid extraction. Results obtained in this study were in good agreement with those obtained using liquid-liquid extraction demonstrating that the recommended procedure was a fast, accurate and stable sample pretreatment method obtaining good efficiency for the extraction of organophosporus insecticides from strawberries and cherries.

Fragaria↗
PubMed1998

Headspace solid-phase microextraction for the determination of volatile and semi-volatile pollutants in water and air.

In this work we report the use of solid-phase microextraction (SPME) to extract and concentrate water-soluble volatile as well as semi-volatile pollutants. Both methods of exposing the SPME fibre were utilised: immersion in the aqueous solution (SPME) and in the headspace over the solution (HSSPME). The proposed HSSPME procedure was compared to conventional static headspace (HS) analysis for artificially spiked water as well as real water samples, which had been, equilibrated with various oil and petroleum products. Both techniques gave similar results but HSSPME was much more sensitive and exhibited better precision. Detection limits were found to be in the sub-ng/ml level, with precision better than 5% R.S.D. in most cases. To evaluate the suitability of SPME for relatively high contamination level analysis, the proposed HSSPME method was applied to the screening of run-off water samples that had heavy oil suspended in them from a tire fire incident. HSSPME results were compared with liquid--liquid extraction. Library searches were conducted on the resulting GC-MS total ion chromatograms to determine the types of compounds found in such samples. Both techniques found similar composition in the water samples with the exception of alkylnaphthalenes that were detected only by HSSPME. A brief study was carried out to assess using SPME for air monitoring. By sampling and concentrating the volatile organic compounds in the coating of the SPME fibre without any other equipment, this new technique is useful as an alternative to active air monitoring by means of sampling pumps and sorbent tubes.

Air Pollutants↗
PubMed2001

Measurement of insecticide uptake and effective fraction in a beneficial insect using solid-phase microextraction.

The determination of insecticide uptake in beneficial insects is important for quantifying the doses that are responsible for the toxicological effects and to compare them with the doses that insects may absorb in treated fields. Because of the small size of some beneficial species, the amount of insecticide absorbed may be very low. Herein, we present a method that relies on the sensitivity and specificity of SPME (solid-phase microextraction) as a sampling technique that can be used to measure very small amounts of an organophosphorus insecticide in small insects. In our study, the method was applied to quantify the internal dose and free dissolved fraction of chlorfenvinphos in beneficial parasitoids exposed through a topical application. Up to 0.5 ng of the insecticide could be quantified in these fractions, that is, 10 times less than when using solvent extraction techniques. The penetration and elimination rates of the insecticide in the insect were also determined. The method proved to be suitable to quantify internal doses in parasitoids collected in a treated field.

Animals↗
PubMed2002

Systemic availability and pharmacokinetics of thymol in humans.

Essential oil compounds such as found in thyme extract are established for the therapy of chronic and acute bronchitis. Various pharmacodynamic activities for thyme extract and the essential thyme oil, respectively, have been demonstrated in vitro, but availability of these compounds in the respective target organs has not been proven. Thus, investigation of absorption, distribution, metabolism, and excretion are necessary to provide the link between in vitro effects and in vivo studies. To determine the systemic availability and the pharmacokinetics of thymol after oral application to humans, a clinical trial was carried out in 12 healthy volunteers. Each subject received a single dose of a Bronchipret TP tablet, which is equivalent to 1.08 mg thymol. No thymol could be detected in plasma or urine. However, the metabolites thymol sulfate and thymol glucuronide were found in urine and identified by LC-MS/MS. Plasma and urine samples were analyzed after enzymatic hydrolysis of the metabolites by headspace solid-phase microextraction prior to GC analysis and flame ionization detection. Thymol sulfate, but not thymol glucuronide, was detectable in plasma. Peak plasma concentrations were 93.1+/-24.5 ng ml(-1) and were reached after 2.0+/-0.8 hours. The mean terminal elimination half-life was 10.2 hours. Thymol sulfate was detectable up to 41 hours after administration. Urinary excretion could be followed over 24 hours. The amount of both thymol sulfate and glucuronide excreted in 24-hour urine was 16.2%+/-4.5% of the dose.

Administration, Oral↗
PubMed2000

Solid-phase microextraction for the assay of levomepromazine in human plasma.

Solid-phase microextraction (SPME) was investigated as sample preparation for the assay of the neuroleptic drug levomepromazine in human plasma. A mixture of human plasma, water, chloramitriptyline as internal standard, and aqueous NaOH was extracted with a 100-microm polydimethylsiloxane (PDMS) fiber (Supelco). The desorption of the fiber was performed in the injection port of a gas chromatograph at 260 degrees C [HP 5890; BPX-5 (SGE): 30 m x 0.53 mm ID, 1-microm film capillary; nitrogen-phosphorus selective detection]. As repeatedly found for SPME analysis of drugs in plasma, the recovery was low (i.e., 7% for levomepromazine). However, the analyte and internal standard were well separated and the calibration was linear from 5 to 180 ng/mL. The within-day precision was 2%, 4%, and 19% at concentrations of 160 ng/mL, 80 ng/mL, and 5 ng/mL, respectively. The between-day precision was 3%, 7%, and 19%, respectively. The limit of determination was 5 ng/mL. The comparison with an established liquid-liquid extraction gas-liquid chromatography method revealed good agreement for spiked samples and patient samples. No interfering peaks of drugs coadministered with levomepromazine or of endogenous substances were found. It is concluded that the method can be used in the therapeutic drug monitoring and clinical toxicology of levomepromazine.

Antipsychotic Agents↗
PubMed2004

A novel approach based on solid phase microextraction gas chromatography and mass spectrometry to the determination of highly reactive organic compounds in cells cultures: styrene oxide.

A solid phase microextraction (SPME) gas chromatography/mass spectrometry (GC/MS) method was developed to assess actual doses of highly reactive organic compounds like styrene oxide (SO) in exposed cell cultures. Using SPME, we set up a method to measure accurately extracellular SO concentrations as well as to obtain an approximate assessment of intracellular levels. The SPME-GC/MS method was developed and validated using two different coating materials, carboxen-PDMS and polyacrylate. In cell-free systems, linearity was established over 3 orders of magnitude for both fibers, but carboxen-PDMS showed higher extraction efficiency and a lower limit of detection (0.5 x 10(-7) vs 10(-6) M for polyacrylate). Precision calculated as % RSD was within 4-16% for all intra- and interday determinations. Experiments performed to study SO stability in cell-free medium showed a time-dependent decrease in SO concentration (11% of initial the concentration after 24 h), mostly due to the spontaneous hydrolysis of SO into styrene glycol, which was measured by liquid chromatography/tandem mass spectrometry (LC/MS/MS). When the neuronal cell line (SK-N-MC) was exposed to a nominal concentration of 0.3 x 10(-4) M SO, the actual concentration measured in the supernatant was considerably lower and was found to decrease during incubation. Intracellular SO was estimated indirectly, by difference between the amount measured in the medium without cells and in the supernatant of the cell-containing medium.

Acrylates↗
PubMed2005

Application of solid phase microextraction to the determination of strychnine in blood.

A simple and rapid method based on solid phase microextraction (SPME) via direct immersion followed by gas chromatography coupled with electron impact ionization/mass spectrometry (GC/EI-MS) was developed for the determination of strychnine in blood. Papaverine was used as internal standard (I.S.). Two types of fibre coating were tested, 100 microm polydimethylsiloxane and 65 microm Carbowax/Divinylbenzene, the latter giving higher recoveries of the compound. The main factors affecting the SPME process, such as sample dilution (1:10), adsorption and desorption times (20 and 10 min, respectively), carry-over effect (not observed), pH and salt addition (no modifications on pH or salt concentration) were optimized. The procedure was validated in terms of linearity (r(2)=0.9992 for concentrations ranging from 0.10 to 5.00 microg/mL), intra and interday precision (0.93 and 4.62%, respectively at 0.50 microg/mL; 3.33 and 8.06%, respectively at 2.50 microg/mL), sensitivity (6.83 and 8.91 ng/mL for LOD and LOQ, respectively) and extraction recovery (0.54 and 0.39% at 0.50 and 2.50 microg/mL, respectively). The developed procedure was found suitable for forensic investigations and was considered a good alternative to the liquid-liquid extraction methods normally used for the determination of this compound in biological media.

Adsorption↗
PubMed2001

Biotransformation of (S)-(+)-linalool by Aspergillus niger: an investigation of the culture conditions.

The biotransformation of (S)-(+)-linalool by different Aspergillus niger strains was studied, using submerged shaken liquid cultures. One strain, A. niger DSM 821, was able to convert the substrate to cis- and trans-furanoid linalool oxide (yield 30% and 5%, respectively) and cis- and trans-pyranoid linalool oxide (yield 14% and 1.5%, respectively). The main metabolites, cis-(2S,5R)-furanoid and cis-(3S,6S)-pyranoid linalool oxide, have a sweet, floral, creamy odor and are used in perfumery. The culture conditions involved, such as the composition of the broth and the type and concentration of cosolvent applied and possible adaptation to the substrate during inoculation, were investigated. It was found that (S)-(+)-linalool was converted much better than (R)-(-)-linalool and that no significant chemical conversion of the substrate occurred in control flasks at pH 3.5. Three cosolvents for improving the solubility of linalool in the culture broths were compared, namely MeOH, EtOH, and acetone. The highest bioconversion yields were obtained when the substrate was applied as a diluted solution in acetone. Screening of the fungi for their biotransformation capacity was performed by solid-phase microextraction.

Acyclic Monoterpenes↗
PubMed2002

Analysis of aromatic amines in water samples by liquid-liquid-liquid microextraction with hollow fibers and high-performance liquid chromatography.

Liquid-liquid-liquid microextraction (LLLME) with hollow fibers in high-performance liquid chromatography (HPLC) has been applied as a rapid and sensitive quantitative method for the detection of four aromatic amines (3-nitroaniline, 4-chloroaniline, 4-bromoaniline and 3,4-dichloroaniline) in environmental water samples. The preconcentration procedure was induced by the pH difference inside and outside the hollow fiber. The target compounds were extracted from 4-ml aqueous sample (donor solution, pH approximately 13) through a microfilm of organic solvent (di-n-hexyl ether), immobilized in the pores of a hollow fiber (1.5 cm length x 0.6 mm I.D.), and finally into 4 microl of acid acceptor solution inside the fiber. After a prescribed period of time, the acceptor solution inside the fiber was withdrawn into the microsyringe and directly injected into the HPLC system for analysis. Factors relevant to the extraction procedure were studied. Up to 500-fold enrichment of analytes could be obtained under the optimized conditions (donor solution: 0.1 M sodium hydroxide solution with 20% sodium chloride and 2% acetone; organic phase: di-n-hexyl ether; acceptor solution: 0.5 M hydrochloric acid and 500 mM 18-crown-6 ether; extraction time of 30 min; stirring at 1,000 rev./min). The procedure also served as a sample clean-up step. The influence of humic acid on the extraction efficiency was also investigated, and more than 85% relative recoveries of the analytes at two different concentrations (20 and 100 microg/l) were achieved at various concentration of humic acid. This technique is a low cost, simple and fast approach to the analysis of polar compounds in aqueous samples.

Amines↗
PubMed2002

Method for analysis of 4-hydroxy-2-(E)-nonenal with solid-phase microextraction.

A simple analytical method for 4-hydroxy-2-(E)-nonenal (HNE) using solid-phase microextraction (SPME) fiber was developed. HNE or the derivative of HNE formed by reaction with 2,4-dinitrophenylhydrazine (DNPH) was extracted from the sample solution by immersing the SPME fiber into the solution, and the amount of HNE was quantified by HPLC. The extraction conditions of HNE and HNE-DNPH were examined, using standard solutions, with respect to fiber coating, NaCl concentration, rate of stirring, adsorption temperature, and adsorption time. The recovery of HNE reached 80%, and the quantification limits of HNE and HNE-DNPH using standard compounds were 14.1 pmol/10 mL and 486.5 fmol/10 mL, respectively. This method can be applied to the detection of HNE in oxidized oil or samples of porcine liver.

Aldehydes↗
PubMed2000

Influence of fibre coating in headspace solid-phase microextraction-gas chromatographic analysis of aromatic and medicinal plants.

Solid-phase microextraction (SPME) is a solvent-free technique, which is well established in headspace analysis since it is sensitive, because of the concentration factor achieved by the fibres, and selective, because of different coating materials which can be used. The performance of eight commercially available SPME fibres was compared to evaluate the recoveries of some characteristic components with different polarities and structures present in the headspace of four aromatic and medicinal plants: rosemary (Rosmarinus officinalis L.), sage (Salvia officinalis L.), thyme (Thymus vulgaris L.) and valerian (Valeriana officinalis L.). The relative concentration capacity of each fibre on the same components of each plant was also determined by comparing their abundance with that obtained by classical static-headspace GC. The partition coefficient, K1, between the headspace gaseous phase and SPME polymeric coating, and the relative concentration factors, of some of the characteristic components of the plant investigated dissolved in dibutyl phtalate, were also determined, under rigorously standardised analysis conditions. The results showed that the most effective fibres were those consisting of two components, i.e., a liquid phase (polydimethylsiloxane) and a porous solid (carboxen or divinylbenzene, or both).

Chromatography, Gas↗