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Results for “Solid Phase Microextraction”

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PubMed1999

Chemical characterization and screening of hydrocarbon pollution in industrial soils by headspace solid-phase microextraction.

A headspace solid-phase microextraction method, followed by a gas chromatographic-mass spectrometric analysis, has been developed for the screening of soil samples polluted by coal tar or refined petroleum products. Vapor pressures of target analytes were determined using a capillary GC method to identify environmentally important components with a sufficiently high vapor pressure to be analyzed in the headspace mode. The method was optimized under non-equilibrium conditions with simplicity and automation in mind and does not require any extraction procedure or sample preparation, other than grinding, drying and homogenizing. The analytical performance and the significance of the results for the purpose of chemical characterization, source discrimination, determination of individual isomer distributions and to calculate source or weathering ratios, is discussed.

Gas Chromatography-Mass Spectrometry↗

PubMed2002

Direct determination of benzodiazepines in biological fluids by restricted-access solid-phase microextraction.

A biocompatible solid-phase microextraction (SPME) fiber was prepared using an alkyl-diol-silica (ADS) restricted-access material as the SPME coating. The ADS-SPME fiber was able to simultaneously fractionate the protein component from a biological sample, while directly extracting several benzodiazepines, overcoming the present disadvantages of direct sampling in biological matrixes by SPME. The fiber was interfaced with an HPLC-UV system, and an isocratic mobile phase was used to desorb, separate, and quantify the extracted compounds. The calculated clonazepam, oxazepam, temazepam, nordazepam, and diazepam detection limits were 600, 750, 333, 100, and 46 ng/mL in urine, respectively. The method was confirmed to be linear over the range of 500-50000 ng/mL with an average linear coefficient (R2) value of 0.9918. The injection repeatability and intraassay precision of the method were evaluated over 10 injections, resulting in a RSD of approximately 6%. The ADS-SPME fiber was robust and simple to use, providing many direct extractions and subsequent determination of benzodiazepines in biological fluids.

Anti-Anxiety Agents↗

PubMed2003

Analysis of volatile compounds released during the grinding of roasted coffee beans using solid-phase microextraction.

A dynamic solid-phase microextraction (SPME) method to sample fresh headspace volatile compounds released during the grinding of roasted coffee beans was described and the analytical results using gas chromatography/mass spectrometry (GC/MS) and GC/olfactometry (GC/O) were compared to those of the conventional static SPME sampling methods using ground coffee. Volatile compounds released during the grinding of roasted coffee beans (150 g) were obtained by exposing the SPME fiber (poly(dimethylsiloxane)/divinylbenzene, PDMS/ DVB) for 8 min to nitrogen gas (600 mL/min) discharged from a glass vessel in which the electronic coffee grinder was enclosed. Identification and characterization of volatile compounds thus obtained were achieved by GC/MS and GC/O. Peak areas of 47 typical coffee volatile compounds, separated on total ion chromatogram (TIC), obtained by the dynamic SPME method, showed coefficients of variation less than 5% (n = 3) and the gas chromatographic profile of volatile compounds thus obtained was similar to that of the solvent extract of ground coffee, except for highly volatile compounds such as 4-hydroxy-2,5-dimethyl-3(2H)-furanone and 4-ethenyl-2-methoxyphenol. Also, SPME dilution analysis of volatile compounds released during the grinding of roasted coffee beans showed linear plots of peak area versus exposed fiber length (R (2) > 0.89). Compared with those of the headspace volatile compounds of ground coffee using GC/MS and GC/O, the volatile compounds generated during the grinding of roasted coffee beans were rich in nutty- and smoke-roast aromas.

Chromatography, Gas↗

PubMed2004

Determination of enantiomers of synthetic pyrethroids in water by solid phase microextraction - enantioselective gas chromatography.

Solid phase microextraction (SPME) is an ideal sample preparation technique because of its speed and solvent-free features. Sampling by SPME is selective and only the dissolved concentration is measured, which allows measurement of the bioavailable fraction of a contaminant in aqueous media. One potential application of SPME is for analysis of enantiomers of chiral contaminants in environmental samples. In this study, a method was developed for determining enantiomers of (Z)-cis-bifenthrin and cis-permethrin in water using coupled SPME and enantioselective gas chromatography (GC). Following SPME sampling, enantiomers of (Z)-cis-bifenthrin and cis-permethrin were separated at the baseline on a beta-cyclodextrin-based enantioselective column, and analyte enrichment onto the SPME fiber was not enantioselective. The GC response increased as sampling time was increased from 0 to 240 min, and as sampling temperature was increased from 20 to 40 degrees C. Organic solvents such as methanol, acetone, and acetonitrile enhanced, while soil extracts slightly decreased, the GC response. The integrated SPME-enantioselective GC method was used to analyze surface runoff samples. The analysis showed preferential degradation of the 1S-3S enantiomer over the 1R-3R enantiomer for both (Z)-cis-bifenthrin and cis-permethrin. The concentrations detected by SPME-GC were substantially smaller than those determined following solvent extraction, suggesting that SPME-enantioselective GC analysis selectively measured the dissolved fraction.

Chromatography, Gas↗

PubMed2003

A simple calibration procedure for volatile organic compounds sampling in air with adsorptive solid-phase microextraction fibres.

Adsorptive solid-phase microextraction (SPME) fibres have proven to be a reliable means of sampling volatile organic compounds (VOCs) in air. In this work, polydimethylsiloxane/carboxen (PDMS/CAR) fibres were used to test a new approach of air sampling strategy with SPME in the lab which could lighten calibration procedure and enhance the use of this already rapid, simple, convenient and cost effective sampling technique. Indeed, only one curve can be used whatever the extraction time chosen by the analyst under constant conditions of air velocity and temperature. Ficks' law of diffusion was used to model SPME grab sampling when the fibre was totally exposed to the air sample. Experimental sampling rates were then determined by GC-FID for different sampling conditions, i.e. in a flowing air stream of known velocity ("dynamic mode") and in a stagnant air ("static mode"). These sampling rates were found to be 3.50 and 17.80 mL min(-1) for acetone, 4.06 and 21.20 mL min(-1) for 1,2-dichloroethane, 5.10 and 27.80 mL min(-1) for toluene and 5.36 and 30.80 mL min(-1) for butyl acetate, for static and dynamic sampling modes respectively. Deviation from linearity of the calibration curves, indicating that a significant fraction of the adsorption sites are occupied, were determined. They were found to be approximately equal to 0.9, 1.57, 3.82 and 4.37 nmol for acetone, dichloroethane, toluene and butyl acetate, respectively. Experimentally determined sampling rates of these isolated compounds were also valid when a complex equimolar gaseous mixture was investigated, but deviation from linearity appears earlier. Then, for a given application, sampling times should be chosen very carefully to avoid competitive adsorption and hence, bad quantitative analysis results.

Air Pollutants↗

PubMed2006

Analysis of organophosphorus pesticides in whole milk by solid phase microextraction gas chromatography method.

Solid phase microextraction (SPME) was used for the extraction of residual coumaphos and dichlorvos in whole milk. The residues were analyzed by capillary gas chromatography equipped with nitrogen phosphorus detector (GC-NPD). A manual SPME holder with a 100-microm polyacrylate fiber was used. The optimized conditions for extraction by SPME method were: sample agitation, absorption temperature of 30 degrees C, absorption time of 40 min, desorption time of 10 min, and sample volume was 16.0 mL in the vial. Under these conditions, the calibration graphs were linear in the range of 0.17 microgL-1 to 1.75 microgL-1 for coumaphos and 0.69 microgL-1 to 6.90 microgL-1 for dichlorvos. Precision was good with RSD values of 13% for coumaphos and 14% for dichlorvos. The detection limits (LOD) were 0.060 microgL-1 for dichlorvos and 0.052 for coumaphos. The quantification limits (LOQ) were 0.086 microgL-1 for dichlorvos and 0.066 microgL-1 for coumaphos. The results obtained in this study suggest that SPME is a suitable technique for residual pesticide analysis of milk. The data demonstrate that particular OP pesticides used in dairy farming in the region of Minas Gerais were found to contaminate cow whole milk, and the residues are not removed by treating the milk by boiling.

Adsorption↗

PubMed2002

Evaluation of indoor exposition to benzene, toluene, ethylbenzene, xylene, and styrene by passive sampling with a solid-phase microextraction device.

A solid-phase microextraction (SPME) sampling method is developed to evaluate indoor exposure to benzene, toluene, ethylbenzene, xylene, and styrene with gas chromatography and flame ionization detection for quantitative analysis. An SPME holder with a 100-pm polydimethylsiloxane (PDMS) and 65-pm PDMS-divinylbenzene fiber coating is tested in different air relative humidity conditions. The method gives good resolution, shows a linear response, is repeatable, and presents high sensitivity. This method is compared with National Institute of Occupational Safety and Health (NIOSH) active sampling.

Journal Article↗

PubMed2000

Solid-phase microextraction coupled with high performance liquid chromatography: a complementary technique to solid-phase microextraction-gas chromatography for the analysis of pesticide residues in strawberries.

Solid-phase microextraction coupled with high performance liquid chromatography has been studied for the analysis of methiocarb, napropamide, fenoxycarb and bupirimate in strawberries. The strawberries were blended and centrifuged. Then, an aliquot of the resulting extracting solution was subjected to solid-phase microextraction (SPME) on a 60 microns polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibre for 45 min at room temperature. The extracted pesticides on the SPME fibre were desorbed into SPME/high performance liquid chromatography (HPLC) interface for HPLC analysis with diode-array detection (DAD). The method is organic solvent-free for the whole extraction process and is simple and easy to manipulate. The detection limits were shown to be at low microgram kg-1 level and the linear response covered the range from 0.05 to 2 mg kg-1 of pesticides in strawberries with a regression coefficient larger than 0.99. A good repeatability with RSDs between 2.92 and 9.25% was obtained, depending on compounds.

Chromatography, Gas↗

PubMed2003

Determination of amphetamines in human urine by headspace solid-phase microextraction and gas chromatography.

Solid-phase microextraction (SPME) is under investigation for its usefulness in the determination of a widening variety of volatile and semivolatile analytes in biological fluids and materials. Semivolatiles are increasingly under study as analytical targets, and difficulties with small partition coefficients and long equilibration times have been identified. Amphetamines were selected as semivolatiles exhibiting these limitations and methods to optimize their determination were investigated. A 100- micro m polydimethylsiloxane (PDMS)-coated SPME fiber was used for the extraction of the amphetamines from human urine. Amphetamine determination was made using gas chromatography (GC) with flame-ionization detection (FID). Temperature, time and salt saturation were optimized to obtain consistent extraction. A simple procedure for the analysis of amphetamine (AMP) and methamphetamine (MA) in urine was developed and another for 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxy-N-methamphetamine (MDMA) and 3,4-methylenedioxy-N-ethylamphetamine (MDEA) using headspace solid-phase microextraction (HS-SPME) and GC-FID. Higher recoveries were obtained for amphetamine (19.5-47%) and methamphetamine (20-38.1%) than MDA (5.1-6.6%), MDMA (7-9.6%) and MDEA (5.4-9.6%).

Amphetamines↗

PubMed2006

Comparison of headspace and direct single-drop microextraction and headspace solid-phase microextraction for the measurement of volatile sulfur compounds in beer and beverage by gas chromatography with flame photometric detection.

Three approaches based on headspace single-drop microextraction (HS-SDME), direct single-drop microextraction (Direct-SDME), and headspace solid-phase microextraction (HS-SPME), have been compared for analyzing volatile sulphur compounds (VSCs) in beer and beverage. Procedures and performance of the three methods have been contrasted through the determination of extraction efficiencies, precision, linearity and limits of detection. The overall process of HS-SDME and HS-SPME was applied to GC-FPD determination of five VSCs in beer and beverage.

Beer↗

PubMed2006

Strategies for interfacing solid-phase microextraction with liquid chromatography.

Solid-phase microextraction (SPME) techniques are equally applicable to both volatile and non-volatile analytes, but the progress in applications to gas-phase separations has outpaced that of liquid-phase separations. The interfacing of SPME to gas chromatographic equipment has been straight-forward, requiring little modification of existing equipment. The requirement of solvent desorption for non-volatile or thermally labile analytes has, however, proven challenging for interfacing SPME with liquid-phase separations. Numerous options to achieve this have been described in the literature over the past decade, with applications in several different areas of analysis. To date, no single strategy or interface device design has proven optimal. During method development analysts must select the most appropriate interfacing technique among the options available. Out of these options three general strategies have emerged: (1) use of a manual injection interface tee; (2) in-tube SPME; and (3) off-line desorption followed by conventional liquid injection. In addition, there has been interest in coupling SPME directly to electrospray ionisation and matrix-assisted laser desorption ionisation (MALDI) for mass spectrometry. Several examples of each of these strategies are reviewed here, and an overview of their use and application is presented.

Chromatography, High Pressure Liquid↗

PubMed2000

Multiple solid-phase microextraction.

Theoretical aspects of multiple solid-phase microextraction are described and the principle is illustrated with the extraction of lidocaine from aqueous solutions. With multiple extraction under non-equilibrium conditions considerably less time is required in order to obtain an extraction yield that is equal to that of one extraction at equilibrium. On the other side, the extraction yield can be increased if multiple extraction is performed with the same total time as is needed for one extraction at equilibrium time. The effect of multiple extraction is strongly dependent on the value of the partition constant and for practical use the length of the desorption time is important. A good agreement between theoretical and experimental data has been obtained. Chromatograms are presented showing the potential of multiple solid-phase microextraction.

Chromatography, Liquid↗

PubMed2005

Preparation of novel solid-phase microextraction fibers by sol-gel technology for headspace solid-phase microextraction-gas chromatographic analysis of aroma compounds in beer.

3-(Trimethoxysilyl)propyl methacrylate (TMSPMA) was first used as precursor as well as selective stationary phase to prepare the sol-gel-derived TMSPMA-hydroxyl-terminated silicone oil (TMSPMA-OH-TSO) solid-phase mircroextraction (SPME) fibers for the analysis of aroma compounds in beer. TMSPMA-OH-TSO was a medium polarity coating, and was found to be very effective in carrying out simultaneous extraction of both polar alcohols and fatty acids and nonpolar esters in beer. The extraction temperature, extraction time, and ionic strength of the sample matrix were modified to allow for maximium sorption of the analytes onto the fiber. Desorption temperature and time were optimized to avoid the carryover effects. To check the matrix effects, several different matrices, including distilled water, 4% ethanol/water (v/v) solution, a concentrated synthetic beer, a "volatile-free" beer and a real beer were investigated. Matrix effects were compensated for by using 4-methyl-2-pentanol as internal standard and selecting the "volatile-free" beer as working standard. The method proposed in this study showed satisfactory linearity, precision and detection limits and accuracy. The established headspace SPME-gas chromatography (GC) method was then used for determination of volatile compounds in four beer varieties. The recoveries obtained ranged from 92.8 to 105.8%. The relative standard deviations (RSD, n = 5) for all analytes were below 10%. The major aroma contributing substances of each variety were identified via aroma indexes.

Beer↗

PubMed2002

Estimation of the main dill seeds odorant carvone by solid-phase microextraction and gas chromatography.

Solid-phase microextraction (SPME) was examined for its suitability for isolation of volatiles from seeds of dill in comparison with the traditional steam distillation procedure. Two main dill seeds volatiles, carvone and limonene, were taken into consideration. Two Supelco SPME fibers were used for the extraction: polyacrylic (PAc) and polydimethylsiloxane (PDMS). The time required to saturate the fibers was 3 min, while distillation took 3 h. Gas chromatography (GC) separation was reduced to 5 min by use of microcapillary column HP-5 cross-linked 5% Ph Me Siloxane. The standards of limonene and carvone were used to prepare calibration curves. PAc fiber responses were described by quadratic curves while PDMS responded linearly. Six varieties of dill were examined by distillation and SPME with both fibers. The good results were achieved for carvone by SPME-PDMS with significant regression between distillation and SPME. This compound can be measured in dill seeds samples within 10 min. The SPME-PDMS were also tested for its application to chiral resolution of carvone and limonene enantiomers in dill seeds oil. The enantiomeric separation was done with two chiral columns. The enantiomeric ratios measured by SPME were just the same as with distillation.

Anethum graveolens↗

PubMed2004

Novel fiber coated with amide bridged-calix[4]arene used for solid-phase microextraction of aliphatic amines.

Solid-phase microextraction (SPME) using a novel fiber coated with 25,27-dihydroxy-26, 28-oxy(2',7'-dioxo-3',6'-diazaoctyl)oxy-p-tert-butylcalix[4]arene/hydroxy-terminated silicone oil has been introduced as a rapid and sensitive pretreatment technique coupled to gas chromatography-flame ionization detection (GC-FID) for the detection of aliphatic amines without derivatization. Due to the introduction of the polar amide bridge in calix[4]arene, the new fiber shows good selectivity and sensitivity to the polar aliphatic amines in addition to its high thermal stability (380 degrees C), solvent stability and good reproducibility between fibers. The extraction temperature, extraction time, pH, and ionic strength of the matrix sample were modified to allow for maximum sorption of the analytes onto the fiber. The method proposed in this study showed satisfactory linearity, precision and detection limits. Practical applicability was demonstrated through the determination of trimethylamine (TMA) in fish tissue. Mean recovery of 92.5% (n = 5) was obtained for the fish extracts and the relative standard deviation was 4.9% (n = 5). The results of fish freshness assay indicate the present method is a validated and simple procedure for the simultaneous determination of TMA in fish.

Amines↗

PubMed2005

Approaches for coupling solid-phase microextraction to nanospray.

Biocompatible solid-phase microextraction (SPME) devices were prepared using two restricted access materials (RAM) as the SPME coating. The restricted access materials were immobilized on steel and platinum wires. The selective coating eliminated most of the matrix interference, which allowed the coupling to mass spectrometry without further purification. The SPME devices were interfaced to mass spectrometry by electronanospray. Several experimental set-ups are described and discussed herein. For the in situ extraction of peptides from the tryptic digests, trypsin was immobilized both on steel wires and on the inside wall of a vial. The devices were incubated together with the RAM-SPME devices and a protein (casein) solution. After the protein digestion, the resulting peptides were analyzed by SPME/nanospray. The vial approach provided the best results; up to eight peptides could be identified which corresponds to a sequence coverage of 58%. The limit of detection of SPME/nanospray for the extraction of peptides from an aqueous solution was about 50 fmol/mL. The results demonstrate that the direct coupling of SPME to nanospray can reduce analysis time and is an attractive alternative to conventional approaches like Zip-Tip purification.

Amino Acid Sequence↗

PubMed2005

Sensitive quantification of sulfur compounds in wine by headspace solid-phase microextraction technique.

A sensitive solid-phase microextraction and gas chromatography-pulsed flame photometric detection technique was developed to quantify volatile sulfur compounds in wine. Eleven sulfur compounds, including hydrogen sulfide, methanethiol, ethanethiol, dimethyl sulfide, diethyl sulfide, methyl thioacetate, dimethyl disulfide, ethyl thioacetate, diethyl disulfide, dimethyl trisulfide and methionol, can be quantified simultaneously by employing three internal standards. Calibration curves were established in a synthetic wine, and linear correlation coefficients (R2) were greater than 0.99 for all target compounds. The quantification limits for most volatile sulfur compounds were 0.5 ppb or lower, except for methionol which had a detection limit of 60 ppb. The recovery was studied in synthetic wine as well as Pinot noir, Cabernet Sauvignon, Pinot Grigio, and Chardonnay wines. Although the sulfur compounds behaved differently depending on the wine matrix, recoveries of greater than 80% were achieved for all sulfur compounds. This technique was applied to analyze volatile sulfur compounds in several commercial wine samples; methionol concentrations were found at the ppm level, while the concentrations for hydrogen sulfide, methanethiol, and methyl thioacetate were at ppb levels. Only trace amounts of disulfides and trisulfides were detected, and ethanethiol was not detected.

Calibration↗

PubMed2000

Determination of aqueous chlorothalonil with solid-phase microextraction and gas chromatography.

Solid-phase microextraction coupled with GC-electron-capture detection was examined to analyze aqueous chlorothalonil residuals. The optimal conditions for chlorothalonil pre-concentration such as fiber polarity, temperature, salt addition, absorption time, as well as the interference were investigated in detail. In addition, the thermal desorption conditions in the injector were also systematically optimized. Experimental results indicated that an extraction with a 100-microm polydimethylsiloxane fiber for 40 min under conditions of 1250 rpm stirring rate, room temperature, and adding high concentration salt offered an optimal result. The thermal desorption of chlorothalonil at 240 degrees C for 3 min (including fiber regeneration) offered the best sensitive detection. A standard addition method for calibration was recommended to reduce the deviation from matrix interference. The proposed method provided a simple and rapid analytical procedure for chlorothalonil in water bodies with detection limits of 2.86 microg/l for distilled water, 3.06 microg/l for ground water, 4.77 microg/l for tap water, and 9.23 microg/l for farm water. The relative standard deviations were all below 3.0% (n=6) besides the farm water being below 9.2%. The calibration graph in the range of 5 to 200 microg/l is linear with very good correlation coefficient (r=0.999), and r=0.983 for farm water. Application was illustrated by the analysis of water samples collected from tap water, ground water and farm water in the southern Taichung area.

Artifacts↗