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PubMed2005

Determination of pesticides and some metabolites in different kinds of milk by solid-phase microextraction and low-pressure gas chromatography-tandem mass spectrometry.

A new analytical method is proposed to determine more than 40 multiclass pesticides in different kinds of processed (whole, skimmed and powdered) and unprocessed (goat and human) milk samples using solid-phase microextraction (SPME). A comparative study between headspace (HS) and direct immersion (DI) was carried out. The effect of milk dilution and the use of acid to reduce the influence of the matrix in DI-SPME mode were also evaluated. DI of the SPME fiber into previously diluted and acidified milk samples achieved the best sensitivity results. Pesticides were determined using low-pressure gas chromatography-tandem mass spectrometry (LP-GC-MS/MS). Both of the selected techniques have been shown to be effective at reduce fat interference and can determine analytes present at very low concentrations (limits of quantification between 0.02 and 1.00 microg L(-1)). Performance characteristics such as linearity, recovery, precision, and lower limits, together with an estimation of the measurement uncertainty using validation data, are presented for each pesticide. All of the pesticides presented recovery rates of between 81 and 110% and precision values lower than 12% (expressed as the relative standard deviation). The overall uncertainty of the method was estimated at three different concentrations (10, 25 and 50 microg L(-1)) and was lower than 25.5% in all cases. The proposed analytical methodology was applied to the analysis of target pesticides in 35 samples: 15 commercial, 3 human and 17 goat milk samples. The metabolite p,p'-DDE was the compound most frequently found in both the breast and goat milk samples, at concentration levels < 20 microg L(-1). However, pesticide residues were not found in any of the other 15 commercial milk samples (skimmed, powdered and whole milk) analyzed.

Animals↗

PubMed2002

Application of headspace solid-phase microextraction and gas chromatography-mass spectrometry for detection of the chemical warfare agent bis(2-chloroethyl) sulfide in soil.

A field expedient analytical method for detecting the chemical warfare agent (CWA) sulfur mustard as a soil contaminant was developed using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS). Five commercially available SPME fibers were investigated to determine the optimal fiber, and extraction conditions. Polyacrylate and carbowax-divinylbenzene fiber coatings gave a statistically indistinguishable and best response compared to the other three types examined in a simple system studied without soil. The polyacrylate fiber coating was selected for study of a system in which sulfur mustard was spiked to an agricultural soil (Standard Reference Material 2709, San Joaquin type). With soil samples, the greatest sensitivity occurred by the addition of deionized water to spiked soil and extraction at ambient temperature for 20 min or longer. SPME sampling with GC-MS analyses afforded good reproducibility (relative standard deviation between 2 and 10%), and analyte concentrations as low as 237 ng/g were detected in soil (total ion chromatograms). As completed here, total time for sampling and analysis was just under 1 h, and use of organic solvents or special sample introduction equipment was avoided.

Chemical Warfare Agents↗

PubMed1999

Headspace solid-phase microextraction for the determination of benzene, toluene, ethylbenzene and xylenes in urine.

A method for the determination of benzene, toluene, ethylbenzene and xylenes (BTEX) in urine of people exposed to these airborne pollutants present in the living environment, has been described. Solid-phase microextraction has been used for sampling BTEX from the headspace of urine and gas chromatography-mass spectrometry has been applied for the selective analysis of chemicals. The method has the following features: small volume of urine (2 ml) needed, linearity in the range of interest (from the limit of detection up to 5000 ng/l) with coefficient of correlation > or =0.998, limit of detection in the range 12-34 ng/l, good repeatability (coefficient of variation 2-7%), high specificity. The stability of the urine sample during storage (-20 degrees C) was evaluated: BTEX remained stable for up to 2 months. The assay has been successfully applied to the biological monitoring of two subjects environmentally exposed to airborne BTEX in an urban area.

Benzene↗

PubMed2002

Gas-phase analysis of trimethylamine, propionic and butyric acids, and sulfur compounds using solid-phase microextraction.

Complaints due to odors are an important problem for the wastewater, composting, and animal agriculture industries. Accurate, objective measurement techniques are needed to monitor emissions, to develop new waste handling procedures, and to reduce the production of these volatile gases. Solid-phase microextraction was investigated as a technique for the determination of representative odorous gases. A flow-through Teflon chamber was used to expose the fibers to certified gas standards. A 75-microm carboxen-poly(dimethylsiloxane) (Car-PDMS) coating was used for trimethylamine (TMA), carbon disulfide (CS2), dimethylsulfide (DMS), and dimethyl disulfide (DMDS), and an 85-microm polyacrylate coating was used for propionic acid (PA) and butyric acid (BA). Using a 1-h fiber exposure time and a flow rate through the chamber of 72 mL/min, method detection limits were 2.38, 0.074, 0.150, 0.063, 1.85, and 1.32 ppbv for TMA, DMS, CS2, DMDS, PA, and BA, respectively. Enhanced detector signal was observed for all analytes under flow conditions, as compared to static conditions, and the porous nature of the Car-PDMS coating appears to increase the time needed for analytes to reach equilibrium under flow conditions.

Adsorption↗

PubMed2002

Investigation of volatiles evolution during the alcoholic fermentation of grape must using free and immobilized cells with the help of solid phase microextraction (SPME) headspace sampling.

A biocatalyst was prepared by immobilization of Saccharomyces cerevisiae strain AXAZ-1 on delignified cellulosic material (DCM). Repeated batch fermentations were conducted using these biocatalysts and free cells, separately, at temperatures of 20, 15, and 10 degrees C. Solid phase microextraction (SPME) was used in monitoring the formation of volatile alcohols, acetate esters, and ethyl esters of fatty acids. The kinetics of volatile production were similar for free and immobilized cells. In all cases immobilized cells showed a better rate of volatile production, which was directly connected to sugar consumption. The main difference observed was in propanol production, which increased with temperature decrease for the immobilized cells, whereas it remained constant for the free ones. In the case of immobilized cells significant amounts of esters were also produced. It is well-known that esters contribute to the fruity aroma of wine. It was also established that SPME is a very sensitive, accurate, and reliable technique and can be used without any reservation in the characterization of volatile constituents of wine.

Acetaldehyde↗

PubMed1999

Determination of carphedon in human urine by solid-phase microextraction using capillary gas chromatography with nitrogen-phosphorus detection.

Carphedon is a phenyl derivative of nootropil and is effective in increasing physical endurance and cold resistance, and is used for amnesia treatment. Carphedon was extracted from human urine samples by solid-phase microextraction with a 65 microns carbowax-divinylbenzene-coated fiber. This analysis was performed by using capillary gas chromatography with nitrogen-phosphorus detection and optimized at pH 9.6, 30% NaCl, immersion time 10 min and desorption in the GC injector at 250 degrees C for 3 min. The regression equation for carphedon showed good linearity in the range from 0.1 to 10 micrograms ml-1 for human urine samples. The limit of detection was 0.01 microgram ml-1. The developed method is more sensitive and simpler in sample preparation than liquid-liquid extraction and can be applied to doping analysis for stimulants.

Central Nervous System Stimulants↗

PubMed2004

Solid-phase microextraction and gas chromatography-electron capture detection analysis of trace organochlorine pesticides in water using novel benzo-15-crown-5 sol-gel coating.

A novel dihydroxy-terminated benzo-15-crown-5 is synthesized and applied to prepare the solid-phase microextraction (SPME) fiber coating with sol-gel technology. Headspace SPME, as a simple, solvent-free method, is applied to the analysis of 16 organochlorine pesticides (OCPs) present at trace levels in a water sample. A homemade crown ether fiber coated with 80- micro m thickness was used for extraction. Analyses are performed using gas chromatography-electroncapture detection. The optimization of the extraction process is studied. Compared with commercially available SPME fibers, polydimethylsiloxane, the new phases show better selectivity and sensitivity toward OCPs. The linear concentrations range from 1 to 1000 ng/L, the detection limits are in the range of 0.01-0.5 ng/L, the recoveries are over 85%, and relative standard deviations are below 7.2% for these OCPs.

Chromatography, Gas↗

PubMedDate not supplied

Rapid analysis of amphetamine, methamphetamine, MDA, and MDMA in urine using solid-phase microextraction, direct on-fiber derivatization, and analysis by GC-MS.

A rapid, sensitive, and solvent-free procedure for the simultaneous determination of amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), and 3,4-methylenedioxymethamphetamine (MDMA) in urine was developed using solid-phase microextraction (SPME) and gas chromatography-mass spectrometry (GC-MS) in the selected ion monitoring mode. A headspace vial containing the urine sample, NaOH, NaCl, and amphetamine-d3 as the internal standard was heated at 100 degrees C for 20 min. A polydimethylsiloxane fiber was maintained in the vial headspace for 10 min in order to adsorb the amphetaminic compounds, which were subsequently derivatized by exposing the fiber to trifluoroacetic anhydride for 20 min in the headspace of another vial maintained at 60 degrees C for 20 min. The trifluoroacetyl derivatives were desorbed in the GC injection port for 5 min. Several parameters were considered during the method optimization process. These included a comparison of SPME with or without headspace, the required derivatization procedure, and the influence of temperature on the headspace extraction and derivatization methods. The optimized method was validated for the four compounds tested. Calibration curves showed linearity in the range 50-1000 ng/mL (r = 0.9946-0.9999). Recovery data were 71.89-103.24%. The quantitation limits were 10 ng/mL for amphetamine and methamphetamine and 20 ng/mL for MDA and MDMA. All of these data recommend the applicability of the method for use in the analytical routine of a forensic laboratory.

3,4-Methylenedioxyamphetamine↗

PubMed2006

An improved method for cyanide determination in blood using solid-phase microextraction and gas chromatography/mass spectrometry.

A new method is described for the qualitative and quantitative analysis of cyanide, a very short-acting and powerful toxic agent, in human whole blood. It involves the conversion of cyanide into hydrogen cyanide and its subsequent headspace solid-phase microextraction (HS-SPME) and detection by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring (SIM) mode. Optimizing the conditions for the GC/MS (type of column, injection conditions, temperature program) and SPME (choice of SPME fiber, effect of salts, adsorption and desorption times, adsorption temperature) led to the choice of a 75-microm carboxen/polydimethylsiloxane SPME fiber, with D3-acetonitrile as internal standard, and a capillary GC column with a polar stationary phase. Method validation was carried out in terms of linearity, precision and accuracy in both aqueous solutions and blood. The limit of detection (LOD) and limit of quantitation (LOQ) were determined only in aqueous solutions. The assay is linear over three orders of magnitude (water 0.01-10, blood 0.05-10 microg/mL); and the LOD and LOQ in water were 0.006 and 0.01 microg/mL, respectively. Good intra- and inter-assay precision was obtained, always <8%. The method is simple, fast and sensitive enough for the rapid diagnosis of cyanide intoxication in clinical and forensic toxicology.

Cyanides↗

PubMed2006

Analysing selected VVOCs in indoor air with solid phase microextraction (SPME): a case study.

A multi-storey building with great diversity of room use was monitored after extensive renovation to remove mould growth secondary to a leaky roof. Tests for volatile organic compounds (VOC) with activated charcoal showed a successfully renovation. Solid phase microextraction (SPME) for detection of selected very volatile organic compounds (VVOCs) revealed indoor air concentrations ranging from 550 to 4,600 microg m(-3). The SPME technique also successfully detected emissions from working and building materials and documented the results of remedial measures in offices. The prior and current use of acetone, methyl acetate and 2-methylpentane within the building resulted in their elevated concentrations in other building floors.

Air Pollutants↗

PubMed2005

Indirect determination of low vapour pressures using solid-phase microextraction--application to tetrachlorobenzenes and tetrachlorobenzyltoluenes.

There is still a gap of reliable vapour pressure data at ambient temperature for low volatile organic substances due to the difficult and time-consuming determination using the classical methods. Static headspace extraction with a solid-phase microextraction (SPME) fibre in combination with gas chromatographic analysis provides an inexpensive tool for the indirect determination of low vapour pressures down to 10(-5) Pa. The procedure consists of two steps: (a) exposure of SPME fibre in the headspace above the test chemical over minutes to hours and (b) desorption and quantification of extracted amount. The calibration was performed using low volatile reference substances with well-known vapour pressures. A good correlation was found between substance uptakes of SPME fibre and vapour pressures. The method was applied, e.g. to tetrachlorobenzenes and to selected tetrachlorobenzyltoluenes with questionable vapour pressures. We obtained values between 0.98 and 13.5 Pa for the former and results between 0.13 and 0.68 mPa for the latter group of congeners. The scope of the method can be extended to substances with even lower vapour pressures, provided that reliable reference data are available.

Calibration↗

PubMed2005

Fully automated analysis of estrogens in environmental waters by in-tube solid-phase microextraction coupled with liquid chromatography-tandem mass spectrometry.

A simple, rapid and sensitive method for the determination of five estrogens, estrone, 17beta-estradiol, estriol, ethynyl estradiol, and diethylstilbestrol, was developed using a fully automated method consisting of in-tube solid-phase microextraction (SPME) coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS). These estrogens were separated within 8 min by HPLC using an XDB-C8 column and 0.01% ammonia/acetonitrile (60/40, v/v) at a flow rate of 0.2 mL/min. Electrospray ionization conditions in the negative ion mode were optimized for MS/MS detection of the estrogens. The optimum in-tube SPME conditions were 20 draw/eject cycles of 40 microL of sample using a Supel-Q PLOT capillary column as an extraction device. The extracted compounds were easily desorbed from the capillary by passage of the mobile phase, and no carryover was observed. Using the in-tube SPME LC/MS/MS method, good linearity of the calibration curve (r > or = 0.9996) was obtained in the concentration range from 10 to 200 pg/mL for all compounds examined. The limits of detection (S/N= 3) of the five estrogens examined ranged from 2.7 to 11.7 pg/mL. The in-tube SPME method showed 34-90-fold higher sensitivity than the direct injection method (5 microL injection). This method was applied successfully to the analysis of environmental water samples without any other pretreatment and interference peaks. Several surface water and wastewater samples were collected from the area around Asahi River, and estriol was detected at 35.7 pg/mL in the effluent of a sewage treatment plant. The recoveries of estrogens spiked into river waters were above 86%, except for estriol, and the relative standard deviations were below 0.9-8.8%.

Automation↗

PubMed2002

Methylmercury determination in biological samples by derivatization, solid-phase microextraction and gas chromatography with microwave-induced plasma atomic emission spectrometry.

A method for the extraction and gas chromatographic determination of methylmercury in biological matrices is presented. By combining the advantages of two extraction techniques-microwave-assisted extraction (MAE) and solid-phase microextraction (SPME)--the separation of methylmercury from biological samples is possible. Specifically, the procedure involves microwave extraction with 3 M hydrochloric acid, followed by aqueous-phase derivatization with sodium tetraphenylborate and headspace SPME with a silica fibre coated with polydimethylsiloxane (PDMS). For optimization of the derivatization-SPME procedure, a central composite experimental design with alpha = 1.682 and two central points was used to model gas-chromatographic peak areas as functions of pH, extraction temperature and sorption time. A desirability function was then used for the simultaneous optimization for methylmercury and Hg(II). The optimal derivatization-SPME conditions identified were close to pH 5, temperature 100 degrees C, and sorption time 15 min. The identification and quantification of the extracted methylmercury is carried out by gas chromatography with microwave-induced plasma atomic emission spectrometry detection. The validity of the new procedure is shown by the results of analyses of certified reference materials.

Calibration↗

PubMed2004

Baseline toxicity of a chlorobenzene mixture and total body residues measured and estimated with solid-phase microextraction.

Body residues of compounds with a narcotic mode of action that exceed critical levels result in baseline toxicity in organisms. Previous studies have shown that internal concentrations in organisms also can be estimated by way of passive sampling. In this experiment, solid-phase microextraction (SPME) fibers were used as a tool to estimate the body residues, which were then compared to measured levels. Past application of SPME fibers in the assessment of toxicity risk of samples has focused on separate exposure of fibers and organisms, often necessitated by the amount of agitation needed in order to achieve steady state in the fibers within a convenient time period. Uptake kinetic studies have shown that in SPME fibers with thin coatings, equilibrium concentrations can be reached without agitation within the time frame of a toxicity test. In contrast to toxicity experiments to date, the SPME fibers in the current study were exposed concomitantly to the test water with the organisms, ensuring an exposure under the exact same conditions. Fibers and two aquatic invertebrate species were exposed to a mixture of four chlorobenzenes with a narcotic mode of action. The total body residue of these compounds in the organisms was determined, as was the acute toxicity resulting from the accumulation. The total body residues of both species were correlated to the total concentrations in SPME fibers. It was concluded that toxicity could be predicted based on total body residue (TBR) estimates from fiber concentrations.

Animals↗

PubMedDate not supplied

Determination of furan levels in coffee using automated solid-phase microextraction and gas chromatography/mass spectrometry.

Furan is a 5-member ring chemical with high volatility. Because it is highly volatile, furan levels in foods are not easily determined with accuracy. In this study, an analytical method for furan analysis using an automated solid-phase microextraction system in combination with gas chromatography/mass spectroscopy is described. The performance of the method was demonstrated by the results obtained from a variety of coffees. Furan was detected at part-per-billion levels in coffee. The limit of detection was 0.3 ng/g and limit of quantitation, 0.8 ng/g. The percent recoveries were between 92 and 102.

Calibration↗

PubMed2004

Single drop microextraction or solid phase microextraction-gas chromatography-mass spectrometry for the determination of iodine in pharmaceuticals, iodized salt, milk powder and vegetables involving conversion into 4-iodo-N,N-dimethylaniline.

A rapid sequence of oxidation and iodination using 2-iodosobenzoate as an oxidizing agent and N,N-dimethylaniline as an iodine scavenger at pH 6.4, when 4-iodo-N,N-dimethylaniline is formed, has been used for the determination of iodide by GC-MS. Solid phase microextraction (SPME) and single drop microextraction (SDME) have been used for the extraction of the iodo-derivative and their relative efficiencies compared. Pharmaceutical samples were subjected to solid phase extraction (SPE) for cleanup and the eluate analyzed for iodide. Iodate in salt samples was reduced to iodide with ascorbic acid. Milk powder and dried vegetables were wet combusted with peroxydisulfate to liberate covalently bound iodine as iodate which was reduced before derivatization. A rectilinear calibration graph was obtained for 0.1 microg-10 mg l(-1) iodide by both extraction methods, the correlation coefficient and limit of detection (LOD) were 0.9995 and 25 ng l(-1) iodide by SPME method, and 0.9998 and 10 ng l(-1) iodide by SDME method, respectively. SDME appeared to be more efficient technique than SPME for the present system. From the pooled data, the average recovery of spiked iodide to real samples was 100.7% (range 96.5-107.0%) with an average R.S.D. of 3.1% (range 2.6-4.5%).

Aniline Compounds↗

PubMed2002

Aroma compound analysis of Piper nigrum and Piper guineense essential oils from Cameroon using solid-phase microextraction-gas chromatography, solid-phase microextraction-gas chromatography-mass spectrometry and olfactometry.

The investigation of aroma compounds of the essential oils of dried fruits of black pepper (Piper nigrum) and black and white "Ashanti pepper" (Piper guineense) from Cameroon by means of solid-phase microextraction (SPME) was carried out for the first time to identify the odorous target components responsible for the characteristic odor of these valuable spices and food flavoring products. By means of GC-flame ionization detection (FID) and GC-MS (using different polar columns) the main compounds (concentration >3.0%, calculated as area of GC-FID analysis using a non-polar fused-silica open tubular RSL-200 column) of the SPME headspace samples of P. nigrum (black) and P. guineense (black and white) were found to be: P. nigrum (black)--germacrene D (11.01%), limonene (10.26%), beta-pinene (10.02%), alpha-phellandrene (8.56%), beta-caryophyllene (7.29%), alpha-pinene (6.40%) and cis-beta-ocimene (3.19%); P. guineense (black)--beta-caryophyllene (57.59%), beta-elemene (5.10%), bicyclogermacrene (5.05%) and alpha-humulene (4.86%); and P. guineense (white)--beta-caryophyllene (51.75%), cis-beta-ocimene (6.61%), limonene (5.88%), beta-pinene (4.56%), linalool (3.97%) and alpha-humulene (3.29%). The most intense odor impressions of the essential oils of the various dried pepper fruits were given byprofessional perfumers as follows: P nigrum (black)--fine, pleasant black pepper note; P. guineense (black)--black pepper top-note; and P. guineense (white)--pleasant white pepper note. These analytical results for the SPME headspace samples of three different pepper species from Cameroon are in accordance with the olfactoric data of the corresponding essential oils. A GC-sniffing technique was used to correlate the single odor impression of the identified SPME headspace volatiles of the three investigated pepper samples with the following results: themain compounds such as beta-caryophyllene, germacrene D, limonene, beta-pinene, alpha-phellandrene and alpha-humulene, as well as minor constituents such as delta-carene, beta-phellandrene, isoborneol, alpha-guaiene, sarisan, elemicin, calamenene, caryophyllene alcohol, isoelemicin, T-muurolol, cubenol and bulnesol, are of greatest importance for the characteristic pepper odor notes of these three Piper samples. Further aroma impressions can be attributed to mono- and sesquiterpenes, hexane, octane and nonane derivatives.

Chromatography, Gas↗

PubMed2001

Ethanol-modified subcritical water extraction combined with solid-phase microextraction for determining atrazine in beef kidney.

The determination of the levels of pesticides in food products has prompted the development of sensitive and rapid methods of analysis that are solvent-free or utilize solvents that are benign to the environment and laboratory worker. In this study we have developed a novel extraction method that utilizes ethanol-modified subcritical water in combination with solid-phase microextraction (SPME) for the removal of atrazine from beef kidney. In situ sample cleanup was achieved using the technique of matrix solid-phase dispersion. A cross-linked polymer, XAD-7 HP, was utilized as a dispersing material for kidney samples. Subcritical water extractions were performed with a pressurized solvent extraction unit at 100 degrees C and 50 atm. Experimental parameters investigated were the volume of solvent and amount of modifier required for the complete extraction of atrazine and optimization of the extraction time. It was determined that 30% ethanol in water (v/v) is adequate for the complete extraction of atrazine. A Carbowax-divinylbenzene SPME fiber was used to sample the aqueous extracts. Analysis of the fiber contents was by ion-trap GC/MS utilizing the single ion mode. The total time of analysis for a single kidney sample is 90 min. The average percent recoveries from samples spiked to the concentrations of 2 and 0.2 microg/g were 104 and 111, respectively. The average relative standard deviations were 10 and 9, respectively. The method limit of detection for beef kidney spiked with atrazine was found to be 20 ng/g of sample.

Animals↗