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PubMed2004

Determination of acetone in human breath by gas chromatography-mass spectrometry and solid-phase microextraction with on-fiber derivatization.

Analysis of breath acetone has been used as a diagnostic tool for diabetes. Due to its nature of volatility and activity, it is very difficult to accurately measure the concentration of acetone in human breath by gas chromatography-mass spectrometry (GC-MS). To overcome this problem, we developed a new method using GC-MS and solid-phase microextraction (SPME) with on-fiber derivatization to determine acetone in human breath. Breath gas from controls and diabetic patients was collected in 3-l Tedlar bags. O-2,3,4,5,6-(Pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA) in solution was firstly adsorbed on the SPME fiber of 65 microm polydimethylsiloxane-divinylbenzene (PDMS-DVB), and then the fiber was further headspace exposed in exhaled gas in the Tedlar bag at 40 degrees C for 4 min. Finally, the formed acetone oxime on the fiber was desorbed and analyzed by GC-MS. Using external standard method, acetone in the human breath was quantitatively analyzed by measurement of its oxime. The method provided a low detection limit of 0.049 ppbv for acetone in breath, relative standard deviation (R.S.D.) value of 3.4%, excellent accuracy. In addition, the method required simple sample preparation and no organic solvent. Acetone in diabetic breath was found to be higher than 1.71 ppmv, while its concentration in normal breath was lower than 0.76 ppmv. The results show that GC-MS and SPME with on-fiber derivatization is a simple, rapid and sensitive and solvent-free method for determination of low concentration acetone in breath and analysis of breath acetone can be used as supplementary tool for diagnosis of diabetes.

Acetone↗

PubMed1999

Development of a solid-phase microextraction GC-NPD procedure for the determination of free volatile amines in wastewater and sewage-polluted waters.

An analytical procedure for the determination of free volatile C1-C6 amines in aqueous matrixes has been developed and applied to their determination in waste-water, primary and secondary effluents, and sewage-polluted river samples. The developed analytical procedure involves headspace sampling using solid-phase microextraction with a poly(dimethylpolysiloxane) coating (100 microns) followed by GC-NPD determination and GC/MS confirmation using a tailor-made PoraPLOT amines capillary GC column for volatile amines. Procedural detection limits were compound dependent but ranged from 3 to 56 micrograms L-1, being close to or lower than the odor threshold concentration, and the reproducibility was ca. 15% (N = 5) in real water samples. The developed analytical procedure is solvent free, cost-effective (no cryogenic trap needed), and faster than existing methods because no derivatization step is involved in the determination. Linearity was compound dependent but ranged at least from 50 to 600 micrograms L-1.

Amines↗

PubMed2002

Characterization of wastewater and solids odors using solid phase microextraction at a large wastewater treatment plant.

A simple and reliable technique has been developed and used to detect odorous gases, i.e. propionic and butyric acids, carbon disulfide, dimethyl sulfide, dimethyl disulfide, and trimethylamine, emitted from various materials generated by the wastewater treatment process. The method detection limits are in the low ppb range and comparable to the odor threshold for human detection. In this study solid phase microextraction (SPME) was employed to characterize and quantify odorous compounds in the headspace over samples collected from various unit processes at the District of Columbia Wastewater Treatment Plant, Washington DC, USA. The patterns of odorous chemicals released from wastewater influent, thickened sludge, dewatered sludge and biosolids were evaluated. Volatile reduced sulfurs were more prevalent in samples collected from downstream processes and corresponded with decreased oxidation-reduction potential (ORP) conditions. Volatile fatty acids were consistently identified in the primary gravity thickeners, while trimethylamine could only be detected from biosolids after the post-liming process.

Chemical Phenomena↗

PubMed2005

Determination of microbial volatile organic compounds from Staphylococcus pasteuri against Tuber borchii using solid-phase microextraction and gas chromatography/ion trap mass spectrometry.

The mycelium of Tuber borchii Vittad., a commercial truffle species, is used as a model system for in vitro ectomycorrhizal synthesis, infected seedling production and biotechnological applications. Our fungal cultures were accidentally contaminated with a Staphylococcus pasteuri strain, showing a strong antifungal activity against T. borchii mycelium. In order to identify the antifungal volatile agents produced by S. pasteuri, solid-phase microextraction (SPME) with gas chromatography and mass spectrometry (GC/MS) was used. Using this method 65 microbial volatile organic compounds (MVOCs), synthesized by this bacterium in either single or in fungal-bacterial dual culture, were identified. SPME combined with GC/MS may be a useful method for the determination of MVOCs involved in the antifungal activity. These results showed that bacteria with unusual biological activities could be a major problem during large-scale production of inoculum for truffle-infected seedling.

Fungi↗

PubMed2006

Solid-phase microextraction method for carbon isotopic analysis of volatile carboxylic acids in human plasma by gas chromatography/combustion/isotope ratio mass spectrometry.

A new analytical method is described for the determination of the physiological concentration and low-level enrichment of (13)C-short-chain volatile organic acids (SCVAs) (e.g. (13)C-acetate and (13)C-butyrate) in human plasma. This two-step method involves solid-phase microextraction (SPME) coupled to gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) without any organic solvents or derivatizing agents. Two SCVA extraction methods were compared using a carboxen/polydimethylsiloxane fiber: headspace sampling (HS) and liquid sampling (LS) SPME. The influences of extraction temperature and time were tested to optimize the adsorption of SCVAs onto the fiber. The comparison of the peak area responses of the acids in the two adsorption methods showed better sensitivity in the human physiological concentration range in the LS mode than in the HS mode. The accuracy of isotopic enrichment measurement was determined using plasma spiked with (13)C-acetate and (13)C-butyrate solution from 0 to 1 mol percent excess (MPE). The linearity and repeatability (RSD < 5%) were measured in LS mode. Plasma SCVA concentrations were also determined relative to 3-methylvalerate (internal standard). Linearity and repeatability were observed from 0 to 400 microM for acetate, from 0 to 20 microM for propionate, and from 0 to 10 microM for butyrate. This method was also used to determine plasma acetate production obtained from lactulose (an undigestible disaccharide) fermentation in one healthy volunteer over 3 h. The acetate concentration increased twofold, 2 h after oral lactulose intake. These results are in agreement with the data obtained by GC/MS in healthy volunteers and obese adults following a lactulose intake by using higher amounts of labelled tracers.SPME coupled with GC/C/IRMS can be used to analyze (13)C-SCVAs at low enrichment (<0.5 MPE) within the physiological concentration measured in human plasma.

Algorithms↗

PubMed1999

Identification and characterization of fenton oxidation products of surfactants by ionspray mass spectrometry and solid-phase microextraction gas chromatography mass spectrometry 1. Lauryl sulphate

The Fenton reaction for the degradation of surfactants has been investigated and partial degradation products have been identified and characterized by mass spectrometry for the case of lauryl sulphate. The polar soluble products were investigated by liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization (ESI), and the volatile products leaving the mixture during the reaction were trapped by means of solid-phase microextraction (SPME) and investigated by gas chromatography/mass spectrometry (GC/MS) with electron and chemical ionization. The oxidation leads to the formation of products with hydroxyl and epoxide groups due to insertion of oxygen atoms or to aldehydes derived from the loss of the hydrophilic sulphate group. The extent of mineralization is dependent on peroxide and iron concentrations. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗

PubMed1997

Analysis of 2,4,6-trichloroanisole in wines using solid-phase microextraction coupled to gas chromatography-mass spectrometry.

Cork taint in wine is a serious problem which is exacerbated by the difficulty of its assessment. Current analytical procedures are costly, time consuming and require the use of large amounts of solvents. We developed and evaluated a rapid method for the detection of the cork taint compound, 2,4,6-trichloroanisole (TCA), in wine samples. The method employs solid-phase microextraction, a solventless, automated sampling procedure, coupled to GC-MS-selected ion monitoring analysis. Quantification is enabled by a fully deuterated [2H5]TCA analog used as an internal standard. Accuracy (+/- 8%), precision (R.S.D. 5-13%), and limit of quantification (5 ng/l) are comparable to existing methods.

Anisoles↗

PubMed2005

Solid-phase microextraction measurement of parent and alkyl polycyclic aromatic hydrocarbons in milliliter sediment pore water samples and determination of K(DOC) values.

The U.S. Environmental Protection Agency (EPA) narcosis model for benthic organisms in polycyclic aromatic hydrocarbon (PAH) contaminated sediments requires the measurement of 18 parent PAHs and 16 groups of alkyl PAHs ("34" PAHs) in pore water with desired detection limits as low as nanograms per liter. Solid-phase microextraction (SPME) with gas chromatographic/mass spectrometric (GC/ MS) analysis can achieve such detection limits in small water samples, which greatly reduces the quantity of sediment pore water that has to be collected, shipped, stored, and prepared for analysis. Four sediments that ranged from urban background levels (50 mg/kg total "34" PAHs) to highly contaminated (10 000 mg/kg total PAHs) were used to develop SPME methodology for the "34" PAH determinations with only 1.5 mL of pore water per analysis. Pore water was obtained by centrifuging the wet sediment, and alum flocculation was used to remove colloids. Quantitative calibration was simplified by adding 15 two- to six-ring perdeuterated PAHs as internal standards to the water calibration standards and the pore water samples. Response factors for SPME followed by GC/MS were measured for 22 alkyl PAHs compared to their parent PAHs and used to calibrate for the 18 groups of alkyl PAHs. Dissolved organic carbon (DOC) ranging from 4 to 27 mg/L had no measurable effect on the freely dissolved concentrations of two- and three-ring PAHs. In contrast, 5-80% of the total dissolved four- to six-ring PAHs were associated with the DOC rather than being freely dissolved, corresponding to DOC/water partitioning coefficients (K(DOC)) with log K(DOC) values ranging from 4.1 (for fluoranthene) to 5.6 (for benzo[ghi]perylene). However, DOC-associated versus freely dissolved PAHs had no significant effect on the total "34" PAH concentrations or the sum of the "toxic units" (calculated bythe EPA protocol), since virtually all (86-99%) of the dissolved PAH concentrations and toxic units were contributed by two- and three-ring PAHs.

Benzopyrenes↗

PubMed2006

Quantification of trace volatile sulfur compounds in milk by solid-phase microextraction and gas chromatography-pulsed flame photometric detection.

Volatile sulfur compounds have been reported to be responsible for the sulfurous off-flavors generated during the thermal processing of milk; however, their analysis has been a challenge due to their high reactivity, high volatility, and low sensory threshold. In this study, reactive thiols were stabilized and the volatile sulfur compounds in milk were extracted by headspace solid-phase microextraction, and analyzed by gas chromatography and pulsed-flame photometric detection. Calibration curves for 7 sulfur-containing compounds were constructed in milk by the standard addition technique. Raw, pasteurized, and UHT milk samples with various fat contents were analyzed. Compared with raw and pasteurized samples, UHT milk contained substantially higher concentrations of hydrogen sulfide, methanethiol, carbon disulfide, dimethyl trisulfide, and di-methyl sulfoxide. The high odor activity values calculated for methanethiol and dimethyl trisulfide suggested that these 2 compounds, in addition to di-methyl sulfide reported in a previous study, could be the most important contributors to the sulfurous note in UHT milk.

Animals↗

PubMed2004

Solid-phase microextraction, gas chromatography, and mass spectrometry coupled with discriminant factor analysis and multilayer perceptron neural network for detection of Escherichia coli.

This study was performed to investigate the ability of using discriminant factor analysis (DFA) and an artificial neural network (ANN) to identify and quantify the number of Escherichia coli (ATCC 25922) in nutrient media from data generated by analysis of E. coli volatile metabolic compounds using solid-phase microextraction (SPME) coupled with gas chromatography (GC) and mass spectrometry (MS). E. coli was grown in super broth and incubated at 37 degrees C for 2 to 12 h. Numbers of E. coli were followed using a colony counting method. An SPME device was used to collect the volatiles from the headspace above the samples, and the volatiles were identified using GC-MS. DFA was used to classify the samples from different incubation times. From DFA, it was possible to differentiate super broth from media containing E. coli when cell numbers were 10(5) CFU or more. The potential to predict the number of E. coli from the SPME-GC-MS data was investigated using a multilayer perceptron (MLP) neural network with back propagation training. The MLP comprised an input layer, one hidden layer, and an output layer, with a hyperbolic tangent sigmoidal transfer function in the hidden layer and a linear transfer function in the output layer. Good prediction was found as measured by a regression coefficient (R2 = 0.996) between actual and predicted data.

Colony Count, Microbial↗

PubMed2005

Solid-phase microextraction for qualitative and quantitative determination of migrated degradation products of antioxidants in an organic aqueous solution.

Low molecular weight aromatic substances may migrate out from plastic packaging to their contents, especially if they consist of organic aqueous solutions or oils. It is, therefore, extremely important to be able to identify and quantify any migrated substances in such solutions, even at very low concentrations. We have in this work investigated and evaluated the use of solid-phase microextraction for the specific task of extraction from an organic aqueous solution such as a simulated pharmaceutical solution consisting of 10 vol.% ethanol in water. The goal was furthermore to investigate the possibility of simultaneously identifying and quantifying the substances in spite of differences in their chemical structures. Methods were developed and evaluated for extraction both with direct sampling and with headspace sampling. Difficulties appeared due to the ethanol in the solution and the minute amounts of substances present. We have shown that a simultaneous quantification of migrated low molecular weight degradation products of antioxidants using only one fibre is possible if the extraction method and temperature are adjusted in relation to the concentration levels of the analytes. Comparions were made with solid-phase extraction.

Antioxidants↗

PubMed2002

Determination of organochlorine pesticides in ground water using solid-phase microextraction followed by dual-column gas chromatography with electron-capture detection.

A rapid, sensitive, convenient, and highly quality-assured method is presented for the determination of 19 organochlorine pesticides (OCPs) in small samples (10 ml) of ground water. Samples are initially fortified with 2,4,5,6-tetrachloro-m-xylene (surrogate) and decachlorobiphenyl (retention time marker), then extracted with a 30-micron thickness polydimethylsiloxane solid-phase microextraction fiber. The analytes collected are thermally desorbed in a heated gas chromatographic inlet, separated using independent fused-silica capillary columns ("primary" and "confirmatory"), and detected using electron-capture detection. Two independent statistical procedures were used to evaluate the detection limits, which typically range between 10 and 40 ng l-1, for these analytes. Method performance was also evaluated using two additional protocols employing "performance evaluation" samples, in which authentic ground water samples were fortified to ca. 100 ng l-1 in each of at least six OCPs. The method satisfies additional strict criteria based on uniformity of fiber performance and minimal degradation of the thermally-sensitive analytes endrin and DDT.

Calibration↗

PubMed2000

Determination of isoprene in human expired breath using solid-phase microextraction and gas chromatography-mass spectrometry.

An analytical method for determination of isoprene in expired breath as a marker of body cholesterol synthesis was developed with a special emphasis on breath sampling. Patients were breathing controlled air using respiratory masks for 2 min (washout period) and then their expired breath was collected in 8-1 Tedlar bags. The bags were heated to 40 degrees C and the solid-phase microextraction fiber Carboxen-polydimethylsiloxane 75 microm was inserted through the septum. Extraction time was 10 min. Analytes were desorbed in the GC injector for 2 min at 270 degrees C. Analyses were performed on a Q-PLOT column and fragment ions 68, 67 and 53 were quantified. The concentration range was 1-40 nmol/l, limit of detection was 0.25 nmol/l, the calibration curve was linear. Precision, expressed as RSD, was 5.5-12.5%. These tests are non-invasive, feasible and relatively inexpensive.

Breath Tests↗

PubMed2001

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

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

Animals↗

PubMed2006

Solid-phase microextraction: investigation of the metabolism of substances that may be abused by inhalation.

Purified liquefied petroleum gas (LPG), a mixture of butane, isobutane, and propane, is commonly abused by inhalation. Little is known about the mammalian metabolism of these substances. Metabolism of other hydrocarbons, including n-hexane and cyclohexane, has been studied in vitro using a range of liver preparations, with metabolites analyzed by static headspace techniques. Solid-phase microextraction (SPME) for sampling metabolites in the headspace of incubates of volatile compounds with activated rat liver microsomes is investigated. Cyclohexanol and cyclohexanone were formed from cyclohexane and 1-, 2-, and 3-hexanol and 2-hexanone from n-hexane as predicted. Secondary alcohols are found for the other compounds studied, except for propene and isobutane, together with 2-propanone and 2-butanone from propane and n-butane, respectively. Samples from three individuals who died following LPG abuse contained a range of putative n-butane metabolites: n-butanol, 2-butanol, 2,3-butanediol, 3-hydroxy-2-butanone, and 2,3-butanedione. To our knowledge, the last three compounds have not been proposed as metabolites of n-butane in man. These might be produced through similar metabolic pathways to those of n-hexane and n-heptane. The findings indicate the value of SPME for investigating the metabolism of volatile substances and for detecting and monitoring exposure to these compounds.

Animals↗

PubMed2001

Gc-olfactometry with solid phase microextraction of aroma volatiles from heated and unheated orange juice.

Solid phase micro extraction, SPME, the solventless headspace volatile extraction technique, was combined with GC-olfactometry (GCO) to examine changes in aroma active volatiles when orange juice was heated. Juice volatiles extracted from the static headspace using SPME (carboxen-polydimethylsiloxane fiber) were compared to liquid-liquid extracts. The SPME extract contained a greater proportion of terpenes. Limonene, myrcene and alpha-pinene comprised 86% of total FID peak area whereas they only comprised 24% in the pentane:ether extract. Aroma active volatiles were evaluated by three trained panelists using Osme, a GCO time-intensity procedure. Eighteen aroma active peaks were common to both heat treated and untreated juice headspace extracts. Six peaks were observed only in unheated extracts and five were found only in extracts from heated juices. Relative amounts of acetaldehyde decreased with increasing headspace exposure time and elevated desorption temperatures.

Adsorption↗

PubMed2000

Determination of acetic acid in aqueous samples, by water-phase derivatisation, solid-phase microextraction and gas chromatography.

The direct derivatisation of acetic acid with n-hexyl chloroformate and with benzyl bromide in water was evaluated. With n-hexyl chloroformate, acetic acid did not give the n-hexyl acetate derivative, but the reaction of acetic acid with benzyl bromide in aqueous solution resulted in the formation of benzyl acetate. The derivatisation of acetic acid with benzyl bromide and the headspace solid-phase microextraction (SPME) of benzyl acetate were optimised. Under optimum conditions, the limit of detection for acetic acid was 260 nM, and the relative standard deviation of the overall procedure at 1.10(-4) M acetic acid was 15.6% (n = 10). A linear response was obtained in the 1 x 10(-4) to 5 x 10(-6) M concentration range (R2 = 0.993, n = 6). Although Carbowax-divinylbenzene (CW-DVB)-coated fibres exhibited a higher extraction capacity for benzyl acetate, polyacrylate (PA) was selected, because its mechanical stability was better than that of CW-DVB fibres. Moreover, the relative standard deviation of the SPME was better with PA (1.5%, n = 10 at 1 x 10(-5) M) than with CW-DVB-coated fibres (8.0%, n = 10 at 1 x 10(-5) M). Thus, a new analytical method for the quantitative determination of micromolar concentrations of acetic acid in the aqueous phase was developed. This method is based on water-phase derivatisation with benzyl bromide, headspace SPME with PA fibres and GC-FID. It was observed experimentally that benzyl alcohol formed by hydrolysis of the reagent affected the fibre-gas phase partitioning of benzyl acetate.

Acetic Acid↗

PubMed2006

Solid-phase microextraction of organophosphate pesticides in source waters for drinking water treatment facilities.

The rapid detection of contaminants in our nation's drinking water has become a top homeland security priority in this time of increased national vigilance. Real-time monitoring of drinking water for deliberate or accidental contamination is key to national security. One method that can be employed for the rapid screening of pollutants in water is solid-phase microextraction (SPME). SPME is a rapid, sensitive, solvent-free system that can be used to screen for contaminants that have been accidentally or intentionally introduced into a water system. A method using SPME has been developed and optimized for the detection of seven organophosphate pesticides in drinking water treatment facility source waters. The method is tested in source waters for drinking water treatment facilities in Mississippi and Alabama. Water is collected from a deepwater well at Stennis Space Center (SSC), MS, the drinking water source for SSC, and from the Converse Reservoir, the main drinking water supply for Mobile, AL. Also tested are samples of water collected from the Mobile Alabama Water and Sewer System drinking water treatment plant prior to chlorination. The method limits of detection for the seven organophosphates were comparable to those described in several Environmental Protection Agency standard methods. They range from 0.25 to 0.94 microg/L.

Organophosphorus Compounds↗