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Results for “Solid Phase Microextraction”

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PubMed2006

Solid-phase microextraction coupled with liquid chromatography for determination of beta-carotene in food.

Beta-carotene in vegetables and nutritional products is analyzed using solid-phase microextraction (SPME) coupled with liquid chromatography (LC) to improve the speed of analysis and to reduce the consumption of organic solvents. The relative standard deviations (RSDs) of this analytical method for beta-carotene determinations in vegetables and nutritional products are approximately 10% and 5%, respectively. The amount of beta-carotene was found to vary from 0.35 +/- 0.05 ppm to 76.5 +/- 6.9 ppm for several vegetables in Taiwan. This method was linear over the range of 0.4-40 ppm with correlation coefficients higher than 0.997. The experimentally determined level of beta-carotene in nutritional products varied from 3.8 +/- 0.2 ppm to 24.6 +/- 1.1 ppm following SPME-LC. The recoveries of beta-carotene for these measurements following SPME were all higher than 97% +/- 2% (n = 3). The detection limits of beta-carotene for this method were from 0.027 to 0.054 ppm. Conventional solvent extractions take approximately 4-6 h for extraction and reconcentration but SPME takes approximately 1 h. From several tens to hundreds of milliliters, organic solvents can be saved using SPME. SPME provides better analyses on beta-carotene than conventional solvent extraction for nutritional products in terms of speed, precision, simplicity, and solvent consumption.

Beverages↗

PubMed2003

Determination of cannabinoids in hemp food products by use of headspace solid-phase microextraction and gas chromatography-mass spectrometry.

A fully automated procedure using alkaline hydrolysis and headspace solid-phase microextraction (HS-SPME), followed by on-fiber derivatization and gas chromatographic-mass spectrometric (GC-MS) detection has been developed for determination of cannabinoids in hemp food samples. After addition of a deuterated internal standard, the sample was hydrolyzed with sodium hydroxide and submitted to direct HS-SPME. After absorption of analytes for on-fiber derivatization, the fiber was placed directly into the headspace of a second vial containing N-methyl- N-trimethylsilyltrifluoroacetamide (MSTFA), before GC-MS analysis. Linearity was good for Delta(9)-tetrahydrocannabinol (THC), cannabidiol, and cannabinol; regression coefficients were greater than 0.99. Depending on the characteristics of the matrix the detection limits obtained ranged between 0.01 and 0.17 mg kg(-1) and the precision between 0.4 and 11.8%. In comparison with conventional liquid-liquid extraction this automated HS-SPME-GC-MS procedure is substantially faster. It is easy to perform, solvent-free, and sample quantities are minimal, yet it maintains the same sensitivity and reproducibility. The applicability was demonstrated by analysis of 30 hemp food samples. Cannabinoids were detected in all of the samples and it was possible to differentiate between drug-type and fiber-type Cannabis sativa L. In comparison with other studies relatively low THC concentrations between 0.01 and 15.53 mg kg(-1) were determined.

Cannabinoids↗

PubMed2004

Diffusion-based calibration for solid-phase microextraction of benzene, toluene, ethylbenzene, p-xylene and chlorobenzenes from aqueous samples.

Short-term solid-phase microextraction (SPME) was performed to test a recently proposed semi-empirical model for the prediction of concentrations of analyte in water samples from the fibre-extracted mass without further calibration. The mass uptake rates obtained for benzene, toluene, ethylbenzene and p-xylene (BTEX) differ considerably from the before published, showing that interfibre comparability is a serious issue. The relative prediction errors are between -55% for benzene and +82% for p-dichlorobenzene under optimal conditions, i.e. they are by an order of magnitude higher than originally published. A sensitivity analysis shows the dominant influence of the estimated thickness of the diffusional boundary layer around the fibre on the concentration predicted. Empirical modification of the model equation for this parameter yields satisfactory results under the conditions tested for both BTEX and the selected chlorobenzenes.

Benzene↗

PubMed2006

New approach based on solid-phase microextraction to estimate polydimethylsiloxane fibre coating-water distribution coefficients for brominated flame retardants.

A depletion solid-phase microextraction (SPME) method based on multiple SPME extraction was applied to estimate fibre coating-water distribution constants (Kfs) of brominated flame retardants. Several polybrominated diphenyl ethers (PBDEs) including compounds present in the commercial mixture "Pentamix", and two polybrominated biphenyls (PBBs) were considered as target analytes. One hundred-micrometer poly(dimethylsiloxane) (PDMS) coating fibre was selected to estimate partition coefficients. SPME kinetics studies at 25 and 100 degrees C were performed. Kfs values obtained at both temperatures for brominated flame retardants were compared with the corresponding octanol-water partition coefficients (Kow) values found in literature. A linear log-log relationship between Kow with Kfs was found. To the best of our knowledge, this is the first study where brominated flame retardants Kfs values are estimated.

Bromine↗

PubMed2003

Analysis of virgin olive oil volatile compounds by headspace solid-phase microextraction coupled to gas chromatography with mass spectrometric and flame ionization detection.

The efficiency of headspace solid-phase microextraction (SPME) was evaluated for the qualitative and semi-quantitative analysis of virgin olive oil volatile compounds. The behaviour of four fibre coatings was compared for sensitivity, repeatability and linearity of response. A divinylbenzene-Carboxen-polydimethylsiloxane fibre coating was found to be the most suitable for the analysis of virgin olive oil volatiles. Sampling and chromatographic conditions were examined and the SPME method, coupled to GC with MS and flame ionization detection, was applied to virgin olive oil samples. More than 100 compounds were isolated and characterised. The presence of some of these compounds in virgin olive oil has not previously been reported. The main volatile compounds present in the oil samples were determined quantitatively.

Gas Chromatography-Mass Spectrometry↗

PubMed2000

Headspace solid-phase microextraction and gas chromatographic-mass spectrometric screening for volatile hydrocarbons in blood.

Optimization for headspace solid-phase microextraction (SPME) was studied with a view to performing gas chromatographic-mass spectrometric (GC-MS) screening of volatile hydrocarbons (VHCs) in blood. Twenty hydrocarbons comprising aliphatic hydrocarbons ranging from n-hexane to n-tridecane, and aromatic hydrocarbons ranging from benzene to trimethylbenzenes were used in this study. This method can be used for examining a burned body to ascertain whether the victim had been alive or not when the burning incident took place. n-Hexane, n-heptane and benzene, the main indicators of gasoline components, were found as detectable peaks through the use of cryogenic oven trapping upon SPME injection into a GC-MS instrument. The optimal screening procedure was performed as follows. The analytes in the headspace of 0.2 g of blood mixed with 0.8 ml of water plus 0.2 microg of toluene-d8 at -5 degrees C were adsorbed to a 100-microm polydimethylsiloxane (PDMS) fiber for 30 min, and measured using the full-mass-scanning GC-MS method. The lower detection limits of all the compounds were 0.01 microg per 1 g of blood. Linearities (r2) within the range 0.01 to 4 microg per 1 g of blood were only obtained for the aromatic hydrocarbons at between 0.9638 (pseudocumene) and 0.9994 (toluene), but not for aliphatic hydrocarbons at between 0.9392 (n-tridecane) and 0.9935 (n-hexane). The coefficients of variation at 0.2 microg/g were less than 8.6% (n-undecane). In conclusion, this method is feasible for the screening of volatile hydrocarbons from blood in forensic medicine.

Burns↗

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↗

PubMed2003

Off-line solid-phase microextraction and capillary electrophoresis mass spectrometry to determine acidic pesticides in fruits.

A method based on solid-phase microextraction (SPME) and capillary electrophoresis/mass spectrometry (CE/ MS) is described for determining simultaneously five acidic pesticides (o-phenylphenol, ioxynil, haloxyfop, acifluorfen, picloram) in fruits. The CE device is coupled to an electrospray interface by a commercial sheath-flow adapter. Emphasis is placed on fulfillment of the speed and sensitivity requirements. The best separation is achieved using 32 mM ammonium formate/acid formic buffer at pH 3.1, with a working voltage of 25 kV. The MS detection of the five pesticides was performed in negative ionization mode. Full-scan spectra with base peaks corresponding to [M-H]- were obtained except for acifluorfen, which gives [M-H-CO2]- as most abundant ion. Compared with the conventional EC-UV, the limits of detection were lower for acifluorfen, haloxyfop, ioxynil, and picloram, by a factor of 20, 20, 50, and 2, respectively. Extraction involved fruit sample homogenization with an acetone-water solution (5:1), filtration, and acetone evaporation prior to fiber extraction. SPME conditions such as time, pH, ion strength, stationary phase of the fiber, sample matrix, and desorption solvents were examined. The recovery of the analytes ranged from 7 to 94%, and the relative standard deviation was between 3 and, 13%. The method was found to be linear between 0.02 and 500 mg kg(-1) with correlation coefficients ranging from 0.992 to 0.997. The limits of quantification were from 0.02 to 5 mg kg(-1). The optimized method was successfully applied to the analysis of acid pesticides in fruit samples.

Electrophoresis, Capillary↗

PubMed2004

Development of a solid-phase microextraction gas chromatography/tandem mass spectrometry method for polybrominated diphenyl ethers and polybrominated biphenyls in water samples.

Solid-phase microextraction has been applied for the first time to the determination of trace concentrations of some brominated flame-retardant compounds (BFRs) in water samples. For the development of the method, six polybrominated diphenyl ethers and two polybrominated biphenyls were considered as target analytes. The factors expected to influence the extraction process are fully discussed. Quantification has been performed by gas chromatography/tandem mass spectrometry using an ion trap mass analyzer. This is also the first time that tandem mass spectrometry is applied with these analytes. Unlike conventional methods for BFR analysis, which involve solvent extraction and several cleanup steps before gas chromatography, the proposed method uses headspace extraction and hard contamination of the chromatographic system is prevented. In addition, tandem mass spectrometry provides selectivity and sensitivity in the detection process. The method performs well achieving good linearity (R(2) > 0.997), precision, and detection limits (S/N = 3) ranging from 7.5 to 190 pg/L. The method has been applied to a variety of water samples.

Journal Article↗

PubMed2004

A solid-phase microextraction device for the analysis of electrochemical reaction products by gas chromatography/mass spectrometry.

Presented is a solid-phase microextraction syringe-electrode assembly that may be used to identify electrode reaction products. After an electrochemical experiment, the electrode within this syringe-electrode assembly can be introduced into the injection port of a gas chromatograph. Electrochemical reaction products can be analyzed, provided they adhere to the electrode surface and are amenable to gas chromatographic/mass spectrometric analysis. We highlight the potential usefulness of this device using well-known electrochemical reaction of quinones.

Journal Article↗

PubMed2000

Nonequilibrium solid-phase microextraction for determination of the freely dissolved concentration of hydrophobic organic compounds: matrix effects and limitations.

Solid-phase microextraction (SPME) has recently been applied to measure the freely dissolved concentration, as opposed to the total concentration, of hydrophobic substances in aqueous solutions. This requires that only the freely dissolved analytes contribute to the concentration in the SPME fiber coating. However, for nonequilibrium SPME the sorbed analytes that diffuse into the unstirred water layer (UWL) adjacent to the SPME fiber can desorb from the matrix and contribute to the flux into the fiber. These processes were described as a model. Experimentally, an equilibrated and disconnected headspace was used as a reference for the freely dissolved concentration. The expected contribution of desorbed analytes to the uptake flux was measured for PCB no. 52 in a protein-rich solution, while it was not measured in a matrix containing artificial soil. The latter was possibly due to slow desorption of the analyte from the artificial soil. On the basis of the present study, a contribution of desorbed analytes to the uptake flux is expected only if(1) the rate-limiting step of the uptake process is diffusion through the UWL, (2) the concentration of the sorbed analyte is high, and (3) desorption from the matrix is fast.

Chemical Phenomena↗

PubMed2000

Headspace solid-phase microextraction use for the characterization of volatile compounds in vegetable oils of different sensory quality.

Headspace solid-phase microextraction (HS-SPME) was used to isolate the volatile compounds, which are formed during peroxidation of fatty acids in vegetable oils. Isolated compounds were characterized by GC-MS and quantified using GC with FID detection. Four fibers for HS-SPME method development were tested, and the divinylbenzene/carboxene/PDMS fiber was selected as providing the best detection of analyzed compounds. Extraction curves, limits of detection, repeatability, and linearity were investigated for 14 aldehydes, ketones, hydrocarbons, and alcohols being products of fatty acids autoxidation. Limits of detection for 11 of these were below 1 microg/L. For quantitative purposes, to minimize the influence of temperature on hydroperoxide formation and the changes in the volatiles profile of the extracts, sampling was performed at 20 degrees C. For compound characterization by GC-MS, sampling temperature of 50 degrees C was applied. The developed method was applied to the analysis of refined and cold-pressed rapeseed oil stored at 60 degrees C for 10 days, and for 10 different vegetable oils of various degree of peroxidation. All samples were subjected to sensory analysis. The results of PCA sensory analysis were related to the amount of volatile compounds isolated by SPME method. In cases where the amount of compounds was highest, the samples were perceived as the worst, whereas those with low levels of volatile compounds were the most desired ones according to sensory evaluation. The relation was observed for both total volatiles, quantified C5-C9 aldehydes, and 14 compounds selected in method development. SPME revealed to be a rapid and sensitive method for the extraction and quantitation of trace volatile compounds from plant oils even at ambient temperature.

Alcohols↗

PubMed2002

Solid-phase microextraction of human plasma samples for determination of sufentanil by gas chromatography-mass spectrometry.

A solid-phase microextraction (SPME) method has been developed for the quantitative analysis of sufentanil from human plasma by gas chromatography-mass spectrometry (GC-MS). The immersion SPME sampling technique was optimized for the extraction of sufentanil from plasma. The influence of the pH and the ionic strength of the sample on the extraction of the analytes by the SPME fiber were investigated. Sufentanil and fentanyl (internal standard) were extracted from plasma with a 65-microm polydimethylsiloxane-divinylbenzene (PDMS-DVB) fiber for 30 minutes using salting out agents in basic conditions. The calibration curve was linear over a concentration range of 6-50 ng/mL. Intraday and interday relative standard deviations were 3.6% and 10.6%, respectively. The limit of quantification was 6 ng/mL for a plasma volume of 1 mL. With regard to selectivity, simplicity, and low cost, the SPME method described should be useful for a rapid extraction of sufentanil from human plasma.

Analgesics, Opioid↗

PubMed2005

Headspace solid-phase microextraction as a tool to estimate the contamination of smoked cheeses by polycyclic aromatic hydrocarbons.

Headspace solid-phase microextraction (HS-SPME) was used to study polycyclic aromatic hydrocarbons (PAH) in smoked cheeses. Two types of fiber coatings and different extraction conditions were tested. The results reveal that the use of an 85-microm polyacrylate fiber immersed in the headspace of the samples at 70 degrees C for 60 min is suitable for the detection of PAH with no more than 4 aromatic rings. To determine if a relationship can be established between the results obtained using a solvent extraction technique and HS-SPME, 6 samples of smoked cheese previously studied by a solvent extraction method were analyzed by HS-SPME, and the results obtained by both methodologies were compared. Polycyclic aromatic hydrocarbons were identified and quantified by gas chromatography-mass spectrometry operating in selective ion monitoring mode. Among the PAH determined by the solvent extraction method, only those with 4 aromatic rings or less were detected by HS-SPME and, consequently, this technique does not allow one to determine the PAH content of smoked cheese samples under the conditions of the study. Nevertheless, the relationship between the results obtained by both techniques for some PAH revealed that HS-SPME could be useful as a screening method to distinguish among samples with different degrees of PAH contamination.

Cheese↗

PubMedDate not supplied

Rapid determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in water samples by using solid-phase microextraction followed by gas chromatography with tandem mass spectrometry.

A rapid and simple method of using solid-phase microextraction was developed for determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) in water samples. In this method, the target analyte is extracted from the sample into the polymeric coating of the fused-silica fiber. After exposure, the fiber is thermally desorbed in the heated injection port of the gas chromatograph, and a chromatographic analysis is performed by using low-resolution tandem mass spectrometry. Parameters that may affect the extension of the microextraction process, such as sampling mode, sample volume, temperature, agitation, and sampling time, were studied. Extraction efficiencies for 3 coating fibers were investigated: 100 microm poly(dimethylsiloxane) (PDMS), 65 microm PDMS-divinylbenzene, and 75 microm carboxen-PDMS. Linearity was evaluated (R = 0.999) for a 250-fold concentration range from the fg/mL to the pg/mL level. The 2,3,7,8-TCDD was detected at the fg/mL level when the headspace over the water sample was sampled for 60 min; the limit of detection obtained was better than that of Method 8280B of the U.S. Environmental Protection Agency. The proposed method performed well when applied to the analysis of tap water, lake water, and seawater samples.

Adsorption↗

PubMed2005

Development and validation of a novel method for the analysis of chlorinated pesticides in soils using microwave-assisted extraction-headspace solid phase microextraction and gas chromatography-tandem mass spectrometry.

A new procedure for determining eleven organochlorine pesticides in soils using microwave-assisted extraction (MAE) and headspace solid phase microextraction (HS-SPME) is described. The studied pesticides consisted of mirex, alpha- and gamma-chlordane, p,p'-DDT, heptachlor, heptachlor epoxide isomer A, gamma-hexachlorocyclohexane, dieldrin, endrin, aldrine and hexachlorobenzene. The HS-SPME was optimized for the most important parameters such as extraction time, sample volume and temperature. The present analytical procedure requires a reduced volume of organic solvents and avoids the need for extract clean-up steps. For optimized conditions the limits of detection for the method ranged from 0.02 to 3.6 ng/g, intermediate precision ranged from 14 to 36% (as CV%), and the recovery from 8 up to 51%. The proposed methodology can be used in the rapid screening of soil for the presence of the selected pesticides, and was applied to landfill soil samples.

Gas Chromatography-Mass Spectrometry↗

PubMed2005

[Determination of carbendazim and thiabendazole in tomatoes by solid-phase microextraction coupled with high performance liquid chromatography and fluorescence detection].

A novel method for the determination of carbendazim (MBC) and thiabendazole (TBZ) in tomatoes by solid-phase microextraction (SPME) coupled with high performance liquid chromatography (HPLC) and fluorescence detection was developed. The experimental conditions of SPME, including extraction fiber, extraction time, extraction temperature, desorption time, desorption solvent, desorption mode, pH value, organic solvent and ionic strength, and HPLC conditions were optimized. The SPME for MBC and TBZ was performed on a 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre for 50 min at room temperature with the solution being stirred at 1 100 r/min. The florescence detection was made at 315 nm with excitation wavelength at 280 nm. The method is linear for MBC and TBZ over the range assayed from 0.01 to 1.0 mg/kg tomatoes with the detection limits of 0.003 mg/kg and 0. 001 mg/kg and the correlation coefficients of 0.995 8 and 0.996 7, respectively. The average recoveries for MBC and TBZ were 83.5% and 85.6% with the relative standard deviations (RSDs) of 6.5% and 3.8%, respectively. The method is fast, simple, sensitive, solvent-free and suitable for the determination of MBC and TBZ in tomatoes.

Benzimidazoles↗

PubMed2003

Evaluation of multiple solid-phase microextraction as a technique to remove the matrix effect in packaging analysis for determination of volatile organic compounds.

Multiple solid-phase microextraction (SPME) is an useful technique for the direct quantification of solid samples removing any matrix effect. The volatile organic compounds formed in the extrusion-coating process of multilayer packaging materials have already been quantified by multiple HS-SPME coupled to gas chromatography (GC)-mass spectrometry (MS) using volatile organic compound (VOC) solutions in hexadecane for calibration. In this article, water is proposed as solvent to prepare the calibration solutions because it provides a shorter calibration time, better linearity, better reproducibility, and lower detection limits than hexadecane. Besides, the extraction of VOCs from aqueous solutions is exhaustive and avoids the extrapolations needed to calculate the total peak areas, as they can be calculated as the sum of the individual areas of each extraction. Finally, it is checked whether the two solvents provide the same mean values for the total peak areas.

Gas Chromatography-Mass Spectrometry↗