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Results for “Solid Phase Microextraction”

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PubMed2001

Solid-phase microextraction for the detection of termite cuticular hydrocarbons.

Solid-phase microextraction (SPME)-gas chromatography-mass spectrometry was used to identify the cuticular hydrocarbons of the subterranean termite Coptotermes formosanus Shiraki. Headspace SPME and direct contact SPME methods were evaluated and compared to the hexane extraction method. Variables, such as temperature, time, number of termites, condition of the termites, and the type of SPME fiber were evaluated. Methods were refined to increase the reproducibility as well as the sensitivity. Both SPME methods were successfully used for the identification of all the major termite cuticular hydrocarbons. Using the headspace SPME method, other compounds of interest could also be identified, such as fatty acids. Using the direct contact SPME method, termites could be repeatedly studied over time to monitor chemical changes.

Animals↗

PubMed2003

Monitoring and fast detection of mycotoxin-producing fungi based on headspace solid-phase microextraction and headspace sorptive extraction of the volatile metabolites.

Solid phase microextraction in combination with capillary GC-MS was used as monitoring technique for the collection and detection of the fungal volatile metabolite (+)-aristolochene by sporulated surface cultures of Penicillium roqueforti. A comparison was made between different toxigenic and nontoxigenic strains of P. roqueforti. Different growth conditions and media, such as malt extract agar, potato dextrose agar and sabouraud dextrose agar were compared. Whereas toxigenic strains produced large amounts of (+)-aristolochene, beta-elemene, valencene and germacrene A, nontoxigenic P. roqueforti strains showed a remarkably different headspace profile, in which ethyl-2-hexenoate, E-beta-caryophyllene, aromadendrene and beta-patchoulene were the predominant volatiles, apart from other sesquiterpene hydrocarbons present at lower concentrations. Stir bar sorptive extraction, was also applied in the headspace sampling mode, i.e. headspace sorptive extraction (HSSE) for the enrichment of fungal volatiles from sporulated surface cultures to differentiate between toxigenic and nontoxigenic fungi. Hence, it can be concluded that headspace analysis of volatile fungal metabolites by SPME and HSSE in combination with capillary GC-MS is a suitable monitoring technique for the fast detection of mycotoxin producing fungi.

Gas Chromatography-Mass Spectrometry↗

PubMed2003

Determination of ethylene oxide by solid-phase microextraction device with on-fiber derivatization.

The solid-phase microextraction (SPME) device was used as a time-weighted average (TWA) sampler for ethylene oxide. Carboxen/polydimethylsiloxane (CAR/PDMS) fiber was used and hydrogen bromide (HBr) was loaded onto the fiber. The SPME fiber assembly was then inserted into PTFE tubing to improve the wearer's acceptance as a diffusive sampler. Known concentrations of ethylene oxide around the threshold limit values (TLVs)/time-weighted average and specific relative humidities (RHs) were generated by syringe pumps in a dynamic generation system. Ethylene oxide in gas bags were also generated. An exposure chamber was designed to allow measurement of face velocities, temperatures, exposing vapor concentrations, and RHs. Gas chromatography-mass spectrometry (GC-MS) was used for sample analysis. The appropriate adsorption time for SPME coating HBr was found to be 30 s and the desorption time for 2-bromothanol formed after sampling was determined to be 5 min. The experimental sampling constant of the sampler was found to be (2.96 +/- 0.09) x 10(-2) cm3/min, while face velocity (0-0.25 m/s) as well as RHs (10-80%) were not expected to have effects on the sampler.

Air Pollutants, Occupational↗

PubMed1999

Determination of hydroxyaromatic compounds in water by solid-phase microextraction coupled to high-performance liquid chromatography.

Solid-phase microextraction (SPME) coupled with high-performance liquid chromatography (HPLC) for the analysis of hydroxyaromatic compounds is described. Three kinds of fibers [50 microns carbowax-templated resin (CW-TPR), 60 microns polydimethylsiloxane-divinylbenzene (PDMS-DVB) and 85 microns polyacrylate (PA) fibers] were evaluated. CW-TPR and PDMS-DVB were selected for further study. The parameters of the desorption procedure (such as desorption mode, the composition of the solvent for desorption and the duration of fiber soaking) were studied and optimized. The effect of the structure and physical properties of analytes, carryover, duration of absorption, temperature of absorption, pH and ionic strength of samples were also investigated. The method was applied to environmental samples (lake water) using a simple calibration curve.

Adsorption↗

PubMed2000

Analysis of volatile contaminants in vegetable oils by headspace solid-phase microextraction with carboxen-based fibres.

The headspace solid-phase microextraction (HS-SPME) efficiencies from vegetable oil of the recently available Carboxen-poly(dimethylsiloxane) (PDMS) and divinylbenzene-Carboxen-PDMS fibres were found to be much greater than those of the PDMS fibre for a number of volatile contaminants. Using these Carboxen-based fibres, the commonly used HS-SPME equilibration times for aqueous matrices of 30-45 min at room temperature for a number of halogenated and aromatic analytes with volatilities ranging from 1,1-dichloroethylene to hexachlorobenzene were found to be insufficient for the effective extraction of the less volatile analytes from vegetable oil. HS-SPME at 100 degrees C for 45 min, followed by rapid cooling to 0 degrees C with a 10 min continuing extraction, however, significantly increased the SPME efficiencies for the less volatile analytes. Spiking solutions were prepared in vegetable oil instead of methanol as the latter was found to displace analytes from the Carboxen material. Using either of the Carboxen-based fibres and SPME at 100 degrees C, all the target analytes could be determined at low or sub-microg kg(-1) with repeatability < or =10%, even though an equilibrium SPME of the less volatile analytes was not achieved.

Chromatography, Liquid↗

PubMed2000

Determination of phthalate esters in water samples by solid-phase microextraction and gas chromatography with mass spectrometric detection.

Solid-phase microextraction (SPME) with an 85 microm polyacrylate fiber, coupled to gas chromatography-mass spectrometry was used to determine six phthalate esters and bis(2-ethylhexyl) adipate in water samples. The variables affecting the SPME absorption process were optimized and the method developed was applied to analyze both tap and commercial mineral water samples as well as water from the Ebro river and fishing and industrial ports. For real samples, the linear range in full scan acquisition mode was between 0.02 and 10 microg l(-1) for most compounds, and the limits of detection of the method were between 0.006 and 0.17 microg l(-1). Commercial water samples contained in recipients which were made from different materials were analyzed, and the influence of the material of the recipients on the concentration of phthalates was evaluated.

Esters↗

PubMed2000

Determination of lidocaine in plasma by direct solid-phase microextraction combined with gas chromatography.

Direct-immersion solid-phase microextraction (SPME) has been used to extract the local anesthetic lidocaine from human plasma. A simplified model shows the relationship between the total amount of drug in plasma and the amount of drug extracted. The model takes into account that the drug participates between the fiber, sample and proteins. Therefore the model can also be used to obtain a good approximation of the drug-protein binding. Extraction yields of lidocaine in plasma are <1%, and the protein binding of lidocaine was found to be about 74% at pH 9.5. A SPME method has been developed for the determination of the total amount of lidocaine in plasma. The protein binding was reduced by acidification and, subsequently, the sample was deproteinized with trichloroacetic acid. With a 100-microm polydimethylsiloxane-coated fiber and addition of sodium chloride to the sample an extraction yield of about 12% at equilibrium (45 min) has been obtained. The relative standard deviation of this method is <10%. A linear range was found from 25 to 2000 ng ml(-1) lidocaine in plasma (r=0.998) with a detection limit of 5 ng ml(-1) in plasma. An extraction yield of about 80% could be obtained after an overnight extraction by use of a 65-microm polydimethylsiloxane-divinylbenzene-coated fiber. If an extraction time of 10 min is used with this fiber, the same yield is obtained as with the single-phase fiber in 45 min. However, the drawback of this mixed-phase fiber is its much shorter lifetime.

Anesthetics, Local↗

PubMed2004

Solid-phase microextraction field sampler.

To facilitate the use of solid-phase microextraction (SPME) for field sampling, a new field sampler was designed and tested. The sampler was versatile and user-friendly. The SPME fiber can be positioned precisely inside the needle for time-weighted average sampling or exposed completely outside the needle for grab sampling. The needle is protected within a shield at all times, hereby eliminating the risk of operator injury and fiber damage. A replaceable Teflon cap is used to seal the needle to preserve sample integrity. Factors that affect the preservation of sample integrity (sorbent efficiency, temperature, sealing materials) were studied. The use of a highly efficient sorbent for the fiber is recommended as the first choice for the preservation of sample integrity. Teflon was a good material for sealing the fiber needle, had little memory effect, and could be used repeatedly. To address adsorption of high boiling point compounds on fiber needles, several kinds of deactivated needles were evaluated. RSC-2 fiber needles were the more effective. A preliminary field sampling investigation demonstrated the validity of the new SPME device for field applications.

Adsorption↗

PubMed1998

Determination of cannabinoids in water and human saliva by solid-phase microextraction and quadrupole ion trap gas chromatography/mass spectrometry.

Solid-phase microextraction (SPME) is applied to the determination of cannabidiol, delta 8-tetrahydrocannabinol (delta 8-THC), delta 9-tetrahydrocannabinol (delta 9-THC), and cannabinol in pure water and human saliva. The inherent extraction behavior of the cannabinoids in pure water is evaluated along with optimization of the method in human saliva. The commercially available poly(dimethylsiloxane) (PDMS) SPME fibers were found to be the best class for the cannabinoid analysis. Partition coefficients were found to be extremely large for all of the cannabinoids (log K > 4.0). Equilibrium times for the 7- and 30-micron PDMS fibers were 50 and 240 min, respectively. A shorter extraction time of 10 min with the 30-micron PDMS fiber may be used for multiple extractions from the same vial, thus conserving the sample necessary for analysis and speeding up the total analysis time. Recoveries for the cannabinoids in saliva, relative to pure water, were dramatically improved by a method developed in our laboratory involving addition of glacial acetic acid to the sample vial prior to performing SPME. Using this method, recoveries relative to SPME in pure water ranged from 21 to 47% depending on the cannabinoid. The linear range for spiked saliva samples was established at 5-500 ng/mL (r2 > 0.994) with precisions between 11 and 20% RSD. The ultimate level of detection by SPME for the cannabinoids in saliva was 1.0 ng/mL, with signal-to-noise values of > or = 12. A saliva sample collected 30 min after marijuana smoking was subject to SPME and traditional liquid-liquid extraction analysis. Internal standard quantitation results for delta 9-THC by both methods yielded comparable results, indicating that the SPME method of analysis is highly accurate and precise. The level of delta 9-THC by SPME was found to be 9.54 ng/mL for the saliva sample.

Cannabinoids↗

PubMed2002

Analysis of volatiles from Spanish honeys by solid-phase microextraction and gas chromatography-mass spectrometry.

Headspace solid-phase microextraction (SPME), followed by gas chromatography (GC)-mass spectrometry (MS) determination, has been used for the analysis of honey volatiles. Two SPME fibers were employed to study the composition of volatiles from various types of Spanish honeys. The best results were obtained with the Carboxen/PDMS fiber, using a homogenization time of 1 h at 70 degrees C and a sampling period of 30 min. A total of 35 compounds were detected, most of them identified by GC-MS and quantified using external standards. Differences in the composition of honey volatiles were obtained, and these results allowed the differentiation of honeys. However, further studies are necessary to confirm the utility of this technique as an alternative tool for the characterization of the floral origin of honeys.

Citrus↗

PubMed2003

Accurate determination of 2,4,6-trichloroanisole in wines at low parts per trillion by solid-phase microextraction followed by GC-ECD.

A headspace solid-phase microextraction (HS-SPME) procedure at 30 degrees C with a 100 microm PDMS fiber of a saturated NaCl solution stirred at 1100 rpm combined to GC-ECD for the 2,4,6-trichloroanisol (TCA) determination in wines has been developed. Due to the matrix complexity and ethanol absorption into the fiber, the internal standard selection was crucial to obtain unbiased results. Thus, matrix effects were observed when analyzing different types of Spanish wines (white, early, and vintage red wines) spiked with TCA at low concentration levels (i.e., <40 ng L(-)(1)). In contrast, the use of 2,4,6-tribromoanisole (TBA) as internal standard overcame these matrix effects, whereas the use of 2,4,6-trichlorophenyl ethyl ether led to inconsistent results. The developed HS-SPME-GC-ECD methodology reaches a limit of quantitation for TCA in wine within 2.9-18 ng L(-)(1), with a relative standard deviation of 2.5-13.4%, depending on the TCA concentration level and wine characteristics. This analytical method is comparable to the existing methodologies based on HS-SPME followed by GC-MS in terms of accuracy, precision, length of determination, and length of quantification; however, analysis cost is reduced.

Anisoles↗

PubMed2003

Study of aged cognac using solid-phase microextraction and partial least-squares regression.

Headspace solid-phase microextraction (SPME) and GC-MS were used to analyze 17 commercial French Cognac brandies (9 young and 8 well-aged, ranging in age from 3 to 55 years). Sixty-four volatiles were chosen on the basis of chromatographic separation and/or known odor importance. Chromatographic peaks were manually integrated and the peak area data analyzed using partial least-squares (PLS) regression to study relationships between volatile composition (X variables) and age (Y variable). When only those compounds with the highest significance were included and from these selected the variables (a total of 33) with the highest correlation loadings on the first two principal components, principal component 1 explained 82% of the variance of the measured compounds and 85% of the variance in age. These were considered the most important volatiles to distinguish products of different ages because young and old samples were separated along principal component 1. Norisoprenoids, terpenes, and acetate esters had weaker positive and negative loadings and were therefore left out. The PLS model could predict sample age accurately with the optimum 33 volatiles as well as with a smaller subset consisting of ethyl esters and methyl ketones.

Alcoholic Beverages↗

PubMed2004

Yield effects on 2-methoxy-3-isobutylpyrazine concentration in cabernet sauvignon using a solid phase microextraction gas chromatography/mass spectrometry method.

A rapid and automated solid phase microextraction (SPME) stable isotope dilution gas chromatography/mass spectrometry (GC-MS) method for 2-methoxy-3-isobutylpyrazine (MIBP) quantification in red wine was developed. Wines with 30% (w/v) NaCl and 2-methoxy-(2)H(3)-3-isobutylpyrazine internal standard were sampled with a 2 cm divinylbenzene/carboxen/poly(dimethylsiloxane) SPME fiber for 30 min at 40 degrees C and analyzed by GC-MS. The method was used to measure MIBP concentrations in Cabernet Sauvignon wines that were produced from six winter pruning treatments over two vintages. MIBP concentrations were significantly negatively correlated with buds per vine. In addition, the MIBP concentration was directly related to sensory vegetal intensity ratings obtained by descriptive analysis.

Gas Chromatography-Mass Spectrometry↗

PubMed2006

Microdialysis hollow fiber as a macromolecule trap for on-line coupling of solid phase microextraction and capillary electrophoresis.

On-line coupling of solid phase microextraction (SPME) and capillary electrophoresis (CE) is highly desirable due to the apparent advantages of the two techniques particularly in the context of microanalysis. However, the hyphenation is a significant challenge, because of band broadening and analyte carryover caused by the slow kinetics of analyte desorption in liquid phase. A novel strategy was presented in this study to overcome these problems. Analytes desorbed from an SPME fiber, which was held by an adapter, were first transferred by electrophoretic migration into a short piece of microdialysis hollow fiber, which was located at the inlet of a CE system. Analytes with molecular weights greater than the molecular weight cut-off of the microdialysis material were trapped in the microdialysis hollow fiber due to the dialysis effect. Then, under another electric field with different electrode polarity, the analytes trapped in the microdialysis hollow fiber migrated into the separation capillary and were separated. In the coupling approach, the microdialysis hollow fiber functioned as a macromolecule trap and a sample pre-concentrator as well. Band broadening was eliminated because the initial sample volume was very small (at nL level). Meanwhile, analyte carryover was eliminated because the desorption time could be as long as needed. Coupling of SPME with CE including two modes, capillary zone electrophoresis (CZE) and capillary isoelectric focusing (CIEF), was successfully demonstrated with proteins as test analytes. High efficiency and high resolution were obtained. The detection limits with UV absorbance whole-column imaging detection were 3.0 x 10(-7) and 3.0 x 10(-8) M (S/N = 3) for beta-lactoglobulin A and ovalbumin, respectively.

Journal Article↗

PubMed2002

Adjusted active carbon fibers for solid phase microextraction.

Adjusted active carbon fiber (AACF) was evaluated for Solid Phase Microextraction (SPME), which showed higher sensitivity and stability than traditional coating fibers. The characteristics of AACF result from two different activation methods (chemical and water vapor) and from variable activation conditions (temperature and time). The fiber treated by water vapor appears to have stronger affinity to polar compounds, while that treated by chemical activation appears to have stronger affinity to non-polar compounds. For different target compounds ranged from non-polar to polar, AACF design could be effective with specific selections and sensitivities. As applications in this paper, benzoic acid in soy sauce was extracted onto water-vapor-activated-fiber, then analyzed using gas chromatograph-mass spectrometer (GC-MS). The chemical-activated-fiber SPME was applied in the analysis of benzene series compounds (BTEX) in water matrix. Compared with standard carbon disulfide extraction method, chemical-activated-fiber SPME is more convenient due to its simple process and turns to be of relative low detection limits.

Carbon↗

PubMed2000

Determination of polycyclic aromatic hydrocarbons in sediment using solid-phase microextraction with gas chromatography-mass spectrometry.

Manual solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) is applied for the determination of polycyclic aromatic hydrocarbons (PAHs) from natural matrix through a distilled water medium. Seven of the 16 PAH standards (naphthalene, acenaphthene, fluorene, anthracene, fluoranthene, pyrene, benzo[a]anthracene) are spiked on a marine muddy sediment. The samples, containing PAHs in the range of 10-20 ppm, are then aged at room temperature more than 10 days before analysis. The influence of the matrix, SPME adsorption time, pH, salt content, and SPME adsorption temperature are investigated. The reproducibility of the technique is less than 13% (RDS) for the first 6 considered PAHs and 28% (RDS) for benzo(a)anthracene with a fiber containing a 100-micron poly dimethylsiloxane coating. Linearity extended in the range of 5-50 picograms for PAHs direct injection, 5-70 picograms for PAHs in water, and 1-170 picograms for PAHs in sediment. The detection limit is estimated less than 1 microgram/kg of dry sample for the first 6 considered PAHs in sediment and 1.5 micrograms/kg of dry sample for benzo(a)anthracene using the selected ion monitoring mode in GC-MS. The recoveries of the considered PAHs are evaluated.

Adsorption↗

PubMed2001

Determination of petroleum hydrocarbons in contaminated soils using solid-phase microextraction with gas chromatography-mass spectrometry.

Manual solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry is investigated as a possible alternative for the determination of petroleum hydrocarbons in soils. Spiked onto an agricultural soil is a commercial diesel fuel (DF) with the following composition by weight: 12% linear alkanes, 52% saturated hydrocarbons (branched and cyclic), 21% alkylated aromatic hydrocarbons, 6% polycyclic aromatic hydrocarbons, and 9% unidentified compounds. The spiked soil samples are aged three days at room temperature before analysis. The optimal conditions for the SPME of DF from soils are examined and maximum sensitivity is obtained using a 100-microm polydimethylsiloxane fiber at a sampling temperature of 47 degrees C by sonication both in the headspace and directly through a water medium. The reproducibility of the whole technique showed a relative standard deviation of 10%. The parameters that can influence the recovery of DF (such as the time of SPME extraction, the presence of organic solvent and water, and the matrix) are investigated. The linearity is verified in the range of 40 to 1200 mg/L for the direct injection of DF, 0.1 to 1 mg/L for the SPME of DF from water, and 1 to 50 mg/Kg of dry soil for the SPME of DF from soils. The detection limits are respectively 0.5 mg/L, 0.02 mg/L, and 0.1 mg/Kg of dry soil. The method is corroborated by comparing the results with those obtained by the traditional way.

Journal Article↗

PubMed2003

[Solid phase microextraction and derivatization of sulfide in blood with pentafluorobenzylbromide].

Solid phase microextraction (SPME) and derivatization with pentafluorobenzylbromide for sulfide in blood was presented in the paper. The derivative of sulfide was extracted for 20 min at the condition of room temperature by a polydimethylsiloxane fiber. 1,3,5-tribromobenzene (IS) was used as an internal standerd. GC/MS was used for analysis. The ions at m/z 394 (derivative of sulfide) and m/z 312 (IS) in the selected ion minitoring chromatograms were selected for quantitation. The compound was detectable at least 0.01 microgram/ml. By the determination in poisoning blood, this method would be demonstrated to be simple.

Benzene Derivatives↗