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PubMed2002

Optimisation of solid-phase microextraction of volatiles.

The results of a systematic study on the precision and repeatability of measurements of the headspace solid phase micro-extraction (SPME) with open-cap vials in combination with capillary gas chromatography in comparison with septum-sealed vials are reported. Benzene, toluene, ethylbenzene, and xylene isomers (BTEX) were used as the target analytes in the investigation of spiked water samples at concentration levels of 42.5 microg l(-1). The dependence of a sample volume versus peak area showed maximum SPME recovery. The influence of sample volume on the precision and the time of taking the sample on the losses of volatile analytes was examined.

Hydrocarbons↗
PubMed2003

Identification of 2-bromo-3,4,5,6-tetrachloroaniline and its quantification in the color additives D&C Red Nos. 27 and 28 (phloxine B) using solid-phase microextraction and gas chromatography-mass spectrometry.

The present work describes (a) the identification and characterization of a contaminant, 2-bromo-3,4,5,6-tetrachloroaniline (2BTCA), in the color additives D&C Red Nos. 27 and 28 (phloxine B) and (b) the determination of the extent and level of 2BTCA contamination in certified lots of these colors. For these purposes, 2BTCA (a compound not previously reported in the literature) and its positional isomer 4-bromo-2,3,5,6-tetrachloroaniline (4BTCA) were synthetically prepared. 4BTCA was used as the internal standard for the quantification of 2BTCA in the colors. Test portions from 35 certified lots of D&C Red Nos. 27 and 28 were analyzed for 2BTCA using a solid-phase microextraction-GC-MS method. Those lots were submitted for certification by both domestic (seven) and foreign (four) manufacturers during the past 4 years. Of the test portions analyzed, 22 (62.9%) contained 2BTCA in amounts ranging from 0.15 to 435.7 ppm with an average value of approximately 131.7 ppm. The remaining 13 (37.1%) test portions contained no detectable 2BTCA or less than 0.01 ppm, which is the limit of quantification of the present method. The analyses revealed substantial differences in the level of 2BTCA across lots from the same manufacturer as well as among different manufacturers. The wide range of 2BTCA levels found in the analyzed lots suggests that the presence of 2BTCA in D&C Red Nos. 27 and 28 may be avoided or significantly reduced during the manufacturing process. A direct correlation was observed between the presence of 2BTCA and that of 3,4,5,6-tetrachlorophthalic acid in analyzed batches of D&C Red Nos. 27 and 28. A chemical pathway that could explain the presence of 2BTCA in these color additives, and ways to avoid its formation, are also proposed.

Aniline Compounds↗
PubMed2005

Identification and elimination of polysiloxane curing agent interference encountered in the quantification of low-picogram per milliliter methyl tert-butyl ether in blood by solid-phase microextraction headspace analysis.

Widespread use of the gasoline additive methyl tert-butyl ether (MTBE) and the subsequent human exposure that follows have led to the need to quantify MTBE in a variety of complex biological matrixes. In this work, we demonstrate our latest MTBE quantification assay for whole blood and uncover previously unidentified contamination sources that prevented routine quantification in the low picogram per milliliter (parts per trillion, ppt) range despite a sensitive and selective analytical approach. The most significant and unexpected sources of contamination were found in reagents and laboratory materials most relevant to sample preparation and quantification. In particular, significant levels of MTBE were identified in sample vial septa that use poly(dimethylsiloxane) (PDMS)-based polymers synthesized with peroxide curing agents having tert-butyl side groups. We propose that MTBE is one of the byproducts of these curing agents, which cross-link PDMS via the methyl side groups. Residual MTBE levels of approximately 20 microg/septa are seen in septa whose formulations use these curing agents. Fortunately, these levels can be significantly reduced (i.e., <0.2 ng/septa) by additional processing. Performance achieved with this sample preparation approach is demonstrated using a mass spectrometry-based method to quantify blood MTBE levels in the low-ppt range.

Air Pollutants↗
PubMed1998

Gas-phase postderivatization following solid-phase microextraction for determining acidic herbicides in water.

This study analyzes acidic herbicides from an aqueous sample by developing a methylated postderivatization on the fiber following solid-phase microextration (SPME) with diazomethane gas procedure combined with GC/MS. Analysis results indicate that a silica fiber coated with polyacrylate (PA) yields a higher extraction efficiency than that obtained with poly(dimethylsiloxane) (PDMS) using the SPME technique. Detection limits are achieved at the level of 10-30 ng/L. Linearity is obtained over a wide range, with precision below 12% RSD. In addition, the significant reduction in extraction efficiency is attributed to the concentration of humic acids exceeding 5 mg/L. Various degradation compounds of acidic herbicides in basic solution are also detected, including 2,4-dichlorophenol, 2,4,5-trichlorophenol, 4-chloro-3-methylphenol, pentachlorinated biphenyl, and tetrachlorinated biphenyl. Moreover, the amount of pentachlorinated biphenyl and tetrachlorinated biphenyl increases over time.

Gas Chromatography-Mass Spectrometry↗
PubMed1999

[Application of solid-phase microextraction technique to the detection of amphetamines in urine by GC].

A simple and rapid detection of nine amphetamines co-existing in urine was described. In the test, the method of solid-phase micro-extraction (SPME) by GC technique was used. Urine (1.0 ml), NaCl (0.3 g) and 4-phenylbutylamine (internal standard) were added into a vial (1.5 ml), then the sample was adjusted to pH 12 with 10% NaOH and sealed with a teflon-coated septum. After immersion of the SPME fiber (100 PDME) in the sample for 15 min, the SPME needle was inserted into the injection port of the GC and extruded for 3 min. The result showed that each peak from nine amphetamines compounds and internal standard was clearly separated. The calibration curves were linear from 0.2 to 15 micrograms/ml for most of five amphetamines with r between 0.9928-0.9995. The CV were less 10%. It is concluded that the method is simple, quick, accurate and useful for the practical detection of urine concentration of amphetamines.

Amphetamines↗
PubMed2002

Simultaneous monitoring of volatile selenium and sulfur species from se accumulating plants (wild type and genetically modified) by GC/MS and GC/ICPMS using solid-phase microextraction for sample introduction.

A sensitive method for determining ultratrace volatile Se species produced from Brassica juncea seedlings is described. The use of a new commercially available GC/ ICPMS interface in conjunction with solid-phase micro-extraction is a promising way to perform these studies. The addition of optional gases (O2 and N2) to the argon discharge proved to increase the sensitivity for Se and S as well as for Xe, which as a trace contaminant gas, was used for ICPMS optimization studies. However, the optimization parameters differ when an optional gas is added. In the best conditions, limits of detection ranging from 1 to 10 ppt can be obtained depending on the Se compound and 30 to 300 ppt for the volatile S species. The use of GC/MS with similar sample introduction permits the characterization of several unknown species produced as artifacts from the standards. The method allows the virtually simultaneous monitoring of S and Se species from the headspace of several plants (e.g., onions, garlic, etc.) although the present work is focused on the B. juncea seedlings grown in closed vials and treated with Se. Dimethyl selenide and dimethyl diselenide were detected as the primary volatile Se components in the headspace. Sulfur species also were present as allyl (2-propenyl) isothiocyanate and 3-butenyl isothiocyanate as characterized by GC/MS.

Brassica↗
PubMed2002

Solid-phase microextraction gas chromatography/ion trap mass spectrometry and multistage mass spectrometry experiments in the characterization of germacrene D.

Germacrene D is a vegetable pheromone utilized in interactions among organisms belonging to different species. For the first time, using solid-phase microextraction/gas chromatography/ion trap mass spectrometry, the presence of this compound was detected in an in vitro mycorrhizal synthesis system where the mycelium of the ectomycorrhizal fungus Tuber borchii Vittad. interacts with the plant Tilia Americana L. From this symbiosis, a new structure, called ectomycorrhiza, is formed where the two symbionts exchange nutrients and metabolites. It seems that only after this interaction can the mycelium develop the fruitbody, commonly known as truffle. The results obtained allowed us to ascertain that germacrene D was synthesized by the plant exclusively in the presence of T. borchii. The originality of these data prompted us to hypothesize that this compound could be involved in the first step of ectomycorrhiza formation, as it is able to stimulate specific fungi receptors. In fact, plants release hundreds of secondary metabolites that are important in their interactions with other organisms.

Gas Chromatography-Mass Spectrometry↗
PubMed2003

Rapid screening of 2-[18F]-fluoro-2-deoxy-D-glucose infusions for volatile organic compound contaminants by solid phase microextraction with gas chromatography-selective ion monitoring mass spectrometry (SPME-GC-SIMMS).

A method compatible with radioactive samples, capable of detecting trace volatile components in a sample volume of ca. 1cm(3) of 2-[18F]-fluoro-2-deoxy-D-glucose solution is described. The approach, based on solid phase micro-extraction gas chromatography-mass spectrometry with a carboxen/polydimethylsiloxane based fibre, was optimised with respect to extraction time (10 min), extraction temperature (60 degrees C) and phase volume ratio (1). The analysis time, including extraction, was less than 20 min with linear responses for acetonitrile and ethanol over the ranges: 0.09-80 microg cm(-3) (22 degrees C, acetonitrile) and 0.78-79 microg cm(-3) (22 degrees C, ethanol). The detection limits were estimated to be ca. 0.78 microg cm(-3) for ethanol and 0.09 microg cm(-3) for acetonitrile. Stability studies indicated analyte losses of up to 75% over 24h and analysis of aged 2-[18F]FDG samples showed that levels of ethanol and acetonitrile were not less than 100 microg cm(-3), indicative of levels substantially greater than this in the original infusions given to human subjects.

Calibration↗
PubMed2004

Analytical method for evaluation of exposure to benzene, toluene, xylene in blood by gas chromatography preceded by solid phase microextraction.

Frequency of intentional exposure to organic solvents has been increasing among children and adolescents in Brazil. Analysis of benzene, toluene and xylenes (BTX) in human blood is necessary to diagnose the intentional and accidental exposure to these solvents. A method for BTX determination in blood samples by gas chromatography preceded by solid phase microextration (SPME) from headspace (HS) has been described. SPME has several advantages when compared to other extraction techniques such as simplicity, low cost and solvent-free extraction. The method presents good repeatability (precision was of 2.2-8.0%), accuracy from -4.7 to -9.4%, limit of detection <1.0 ug/mL, linearity from 1.0 to 100 ug/mL for toluene and from 5.0 to 100 ug/mL for the other solvents (R2 > 0.99), which shows to be efficient and adequate for the detection of exposure to BTX in blood samples.

Benzene↗
PubMed2004

Solid-phase microextraction to predict bioavailability and accumulation of organic micropollutants in terrestrial organisms after exposure to a field-contaminated soil.

The risk posed by soil contaminants strongly depends on their bioavailability. In this study, a partition-based sampling method was applied as a tool to estimate bioavailability in soil. The accumulation of organic micropollutants was measured in two earthworm species (Eisenia andrei and Aporrectodea caliginosa) and in 30-microm poly(dimethylsiloxane) (PDMS)-coated solid-phase micro extraction (SPME) fibers after exposure to two field-contaminated soils. Within 10 days, steady state in earthworms was reached, and within 20 days in the SPME fibers. Steady-state concentrations in both earthworm species were linearly related to concentrations in fibers over a 10,000-fold range of concentrations. Measured concentrations in earthworms were compared to levels calculated via equilibrium partitioning theory and total concentrations of contaminants in soil. In addition, freely dissolved concentrations of contaminants in pore water, derived from SPME measurements, were used to calculate concentrations in earthworms. Measured concentrations in earthworms were close to estimated concentrations from the SPME fiber measurements. Freely dissolved concentrations of contaminants in pore water, derived from SPME measurements, were used to calculate bioconcentration factors (BCF) in earthworms. A plot of log BCFs against the octanol-water partition coefficient (log Kow) was linear up to a log Kow of 8. These results show that measuring concentrations of hydrophobic chemicals in a PDMS-coated fiber represents a simple tool to estimate internal concentrations of chemicals in biota exposed to soil.

Animals↗
PubMed1996

Solvent-free sample preparation by headspace solid-phase microextraction applied to the tracing of n-butyl nitrite abuse.

The most common alkyl nitrites encountered in forensic toxicology are iso-butyl, n-butyl and iso-pentyl(amyl) nitrites. All have become popular as an aphrodisiac, especially among the homosexual population. Alkyl nitrites are a volatile and unstable group of compounds, which hydrolyse in aqueous matrices to the alcohol and nitrite ion. Here we describe a fast, clean and sensitive procedure for the detection of hydrolysed n-butyl nitrite in whole human blood using a new, solvent-free sampling technique, the headspace solid-phase micro-extraction (HSPME), combined with GC/FID analysis. Sample preparation was investigated using two different stationary phases (100 microns polydimethylsiloxane and 85 microns polyacrylate), coating a fused silica fibre. The effect of different sampling times at fixed temperatures was also studied. Our results demonstrate that the HSPME/GC/FID procedure allows tracing of n-butyl nitrite abuse and detects hydrolysed n-butyl nitrite, i.e., released n-butanol, in whole blood at the 1 ng/mL level.

Autopsy↗
PubMed2006

Determination of telmisartan in rat tissues by in-tube solid-phase microextraction coupled to high performance liquid chromatography.

A poly(methacrylic acid-ethylene glycol dimethacrylate, MAA-EGDMA) monolithic capillary was used for the direct and on-line extraction of telmisartan from Sprague-Dawley rat tissue (heart, kidney, and liver) homogenates. Under optimized conditions, the tissue homogenates were simply diluted with a mixture of phosphate buffer (pH 2)/ACN (90:8 v/v), and then injected for extraction only after centrifugation and filtration. Coupled to HPLC with fluorescence detection, the method was linear over the range of 1.25-1500 ng/g for telmisartan in heart and kidney, 12.5-15 000 ng/g in liver with correlation coefficients over 0.9992. The detection limits were found to be in the range from 0.24 to 1.8 ng/g. RSDs for intra- and inter-day ranged from 1.2 to 8.1%. The determination of telmisartan in treated rat tissues was achieved by using the proposed method.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2005

Characterization of Spanish unifloral honeys by solid phase microextraction and gas chromatography-mass spectrometry.

Volatile compounds have been investigated in unifloral honeys of the most popular types in Spain. A total of 21 eucalyptus samples, 35 rosemary samples, 33 heather samples, and 15 citrus samples were collected in the course of 3 years in different Spanish regions. Samples were analyzed by SPME followed by GC-MS. About 83 compounds were identified; the concentrations of 33 of them were selected to be processed by multivariate analysis. Discriminant analysis allowed correct assignment of most samples: 94% citrus, 92% eucalyptus, 84% heather, and 84% rosemary. As pure reference honeys are not available, a two step data analysis is proposed, selecting the samples most clearly classified in discriminant analysis as "reference samples" to be used in multiple regression to estimate the most representative compounds for each honey type and considering the rest of the samples as of mixed origin.

Gas Chromatography-Mass Spectrometry↗
PubMed2005

Electrochemical preparation of composite polyaniline coating and its application in the determination of bisphenol A, 4-n-nonylphenol, 4-tert-octylphenol using direct solid phase microextraction coupled with high performance liquid chromatography.

For SPME-HPLC, metal wires with better mechanical strength are preferred over the fused silica fibers. In this article, a novel composite polyaniline (CPANI) doped with PEG and polydimethylsiloxane coating (CPANI fiber) was prepared on a stainless steel wire by a three-electrode system: the fiber was used as the work electrode, a calomel electrode and a platinum electrode were used as the reference and the counter electrodes, respectively. To evaluate the new CPANI coating, the coating was used to extract three kinds of phenols (bisphenol A, 4-n-nonylphenol, and 4-tert-octylphenol) in water samples by direct-SPME mode and then desorbed in commercial SPME-HPLC interface to separation. The extraction procedure was also optimized. Five real water samples were investigated. Good recoveries were gained when environmental samples were analyzed.

Aniline Compounds↗
PubMedDate not supplied

Monitoring seasonal variation in apple fruit volatile emissions in situ using solid-phase microextraction.

Emissions of volatiles from apple fruits (Malus domestica Borkh.) were monitored in situ over the course of a growing season (from early June to mid September) for two apple varieties, Golden Delicious and Maigold. Results indicate a characteristic time-course of volatile emissions as the sampling date was a statistically significant factor for nine of the 13 compounds considered. The amounts of volatiles collected were greatest early and late in the season. The temporal effect on emissions was generally much larger than the effect of variety, which was significant for only four of the 13 compounds considered. The possible sources of variation which are not explained by the statistical models are discussed, and it is considered that they are most likely related to differences in the emissions from individual fruits.

Acetates↗