Determination of fipronil by solid-phase microextraction and gas chromatography-mass spectrometry.

A method for the determination of trace amounts of the insecticide fipronil was developed using solid-phase microextraction-gas chromatography-mass spectrometry and selected ion monitoring. Fipronil was extracted with a fused-silica fiber coated with 85 microm polyacrylate. The effects of pH, ionic strength, sample volume, extraction and desorption times as well as the extraction temperature were studied. Lindane was used as an internal standard. The linear concentration range of application was 0.3-100 ng ml(-1) of fipronil, with a relative standard deviation of 9.5% (for a level of 50 ng ml(-1)) and a detection limit of 0.08 ng ml(-1). The method was applied to check the eventual existence of fipronil above this limit in water and soil samples from Granada (Spain) as well as in human urine samples. The method validation was completed with spiked matrix samples. The method can be applied as a monitoring tool for water, soil and urine, in the investigation of environmental and occupational exposure to fipronil.     

Determination of tebufenpyrad and oxadiazon by solid-phase microextraction and gas chromatography-mass spectrometry

Summary A method for determination of trace amounts of the pesticides tebufenpyrad and oxadiazon, previous solid-phase microextraction (SPME), was developed using gas chromatographymass spectrometry and selected ion monitoring (GC-MS; SIM). Both pesticides were extracted with a fused silica fiber coated with 100 μm polydimethylsiloxane. The effects of pH ionic strength, sample volume, extraction and desorption times as well as extraction temperature were studied. The linear concentration range of application was 0.5–250 ng mL⁻¹ for both compounds, with a detection limit of 0.06 ng mL⁻¹ for tebufenpyrad and 0.02 ng mL⁻¹ for oxadiazon. SPME-GC-MS analysis yielded good reproducibility (RSD between 7.5–10.1%). It was used to check the eventual existence of tebufenpyrad and oxadiazon above this limit in water and soil samples from Granada (Spain) as well as in human urine samples. The method validation was completed with spiked matrix samples. It can be applied as a monitoring tool for water, soil and urine in the investigation of environmental and occupational exposure to tebufenpyrad and oxadiazon.     

Determination of oxadiazon residues by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A method for the determination of trace amounts of the herbicide oxadiazon was developed using headspace solid-phase microextraction (HS-SPME), gas chromatography-mass spectrometry (GC-MS) and selected ion monitoring. It was applied to determine oxadiazon in ground water, agricultural soil, must, wine and human urine samples. To determine oxadiazon in liquid samples, a response surface methodology generated with a Doehlert design was applied to optimize the HS-SPME conditions using a 100 microm polydimethylsiloxane fibre. For the analysis of soil samples, they were mixed with water and the SPME fibre suspended in the headspace above the slurry. Ground water, human urine and must show linear concentration range of application of 0.5-50 ng ml(-1)' with detection limits < or =0.02 ng ml(-1). HS-SPME-GC-MS analysis yielded good reproducibility (RSD values between 6.5 and 13.5%). The method validation was completed with spiked matrix samples. The developed analytical procedure is solvent free, cost effective and fast.     

Partial elucidation of Trichogramma putative sex pheromone at trace levels by solid-phase microextraction and gas chromatography-mass spectrometry studies

Virgin females of the minute parasitoid wasp Trichogramma turkestanica produce about 2 pg/h of two putative sex pheromonal compounds. These compounds could be successfully sampled during 20-50 h with SPME from 1.8 mL vials, containing 50-110 wasps and analysed by GC-MS. Accurate mass measurements at the 1 ng scale were possible with an internal standard of sulphur. One compound with MW 236 was identified as a C17H32 hydrocarbon while the other compound was the corresponding allylic alcohol with composition C17H32O. The alcohol could be silylated on-fibre and its mass spectrum suggested the presence of a conjugated 2,4-diene moiety. A miniaturised solvent extraction system for SPME needles, using 5 microL of acetone in a microtube was developed. After reaction of the extracted volatiles with the dienophile 4-methyl-1,2,4-triazoline-3,5-dione (MTAD), GC-MS of the MTAD adducts confirmed the presence of a diene. Interpretation of the combined mass spectral data, in combination with retention indexes of both compounds on non-polar and polar columns, suggested 2,6,8,12-tetramethyltrideca-2,4-diene and 2,6,8,12-tetramethyltrideca-2,4-dien-1-ol as most probable structures. These compounds have not been described previously. Biogenetically, they are most likely polyketides made up of a C4 starter unit that has been elongated with C2 and C3 units. Further biological and synthetic studies are necessary to prove their role as sex pheromone, confirm the proposed structures and determine the correct stereochemistry of the double bonds and the methyl groups.     

Analysis of chloroacetanilide herbicides in water samples by solid-phase microextraction coupled with gas chromatography-mass spectrometry

A solid-phase microextraction (SPME) method has been developed for the determination of 3 chloroacetanilide herbicides in both fresh and seawater samples. The extracted sample was analyzed by gas chromatography with mass spectrometry detection (GC-MS), and parameters affecting SPME operation including fibre type, sample pH, sample temperature, mixing speed and extraction time have been evaluated and optimized. The amount of dissolved organic matter (DOM) and the salt content both affected SPME extraction efficiency, but the presence of other competitive extractants such as organochlorine pesticides (OCPs) in the matrix showed no insignificance interference. The limit of detection (LOD) for acetochlor, metolachlor and butachlor were 1.2, 1.6 and 2.7 ng L⁻¹, respectively. The recoveries for the herbicides ranged from 79 to 102%, and the linear dynamic range was from 10 to 1000 ng L⁻¹. The developed method has been used to monitor herbicides contaminations in coastal water samples collected around Laizhou bay and Jiaozhou bay in Shandong peninsula, China. The concentrations of acetochlor and metolachlor ranged from undetectable to 78.5 ng L⁻¹ and undetectable to 35.6 ng L⁻¹, respectively. Butachlor was not observed but in only one sample and the concentration is lower than the limit of quantification (LOQ). The concentrations of the three herbicides in this study are low compared to most of the other places reported.     

Determination of cocaine and cocaethylene in urine by solid-phase microextraction and gas chromatography-mass spectrometry

In order to evaluate recent cocaine exposure or its coingestion with ethanol, a simple and sensitive solid-phase microextraction (SPME) procedure for determination of cocaine and cocaethylene in urine was developed and validated. A polydimethylsiloxane fibre (100 microm) was submersed in the urine sample for 20 min under magnetic stirring after alkalinization with solid buffer (NaHCO(3):K(2)CO(3), 2:1). Gas chromatography-mass spectrometry (GC-MS) was used to identify and quantify the analytes in selected ion monitoring mode (SIM). The limits of quantification were 5.0 ng/mL for both analytes. Good inter- and intra-assay precision was also observed (coefficient of variation <9%).     

Determination of amphetamine-type stimulants in oral fluid by solid-phase microextraction and gas chromatography-mass spectrometry

A method for the simultaneous identification and quantification of amphetamine (AMP), methamphetamine (MET), fenproporex (FEN), diethylpropion (DIE) and methylphenidate (MPH) in oral fluid collected with Quantisal? device has been developed and validated. Thereunto, in-matrix propylchloroformate derivatization followed by direct immersion solid-phase microextraction and gas chromatography-mass spectrometry were employed. Deuterium labeled AMP was used as internal standard for all the stimulants and analysis was performed using the selected ion monitoring mode. The detector response was linear for the studied drugs in the concentration range of 2-256 ng mL(-1) (neat oral fluid), except for FEN, whereas the linear range was 4-256 ng mL(-1). The detection limits were 0.5 ng mL(-1) (MET), 1 ng mL(-1) (MPH) and 2 ng mL(-1) (DIE, AMP, FEN), respectively. Accuracy of quality control samples remained within 98.2-111.9% of the target concentrations, while precision has not exceeded 15% of the relative standard deviation. Recoveries with Quantisal? device ranged from 77.2% to 112.1%. Also, the goodness-of-fit concerning the ordinary least squares model in the statistical inference of data has been tested through residual plotting and ANOVA. The validated method can be easily automated and then used for screening and confirmation of amphetamine-type stimulants in drivers' oral fluid.     

Determination of anatoxin-a in environmental water samples by solid-phase microextraction and gas chromatography-mass spectrometry

In the present work, a method was developed and optimized aiming at the determination of anatoxin-a in environmental water samples. The method is based on the direct derivatization of the analyte by adding hexylchloroformate in the alkalinized sample (pH = 9.0). The derivatized anatoxin-a was extracted by a solid-phase microextraction (SPME) procedure, submersing a PDMS fiber in an amber vial for 20 min under magnetic stirring. GC-MS was used to identify and quantify the analyte in the SIM mode. Norcocaine was used as internal standard. The following ions were chosen for SIM analyses (quantification ions in italics): anatoxin-a: 191, 164, 293 and norcocaine: 195, 136, 168. The calibration curve showed linearity in the range of 2.5-200 ng/mL and the LOD was 2 ng/mL. This method of SPME and GC-MS analysis can be readily utilized to monitor anatoxin-a for water quality control.     

Determination of triazines in soil leachates by solid-phase microextraction coupled to gas chromatography-mass spectrometry

A solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) method was developed for the evaluation of the leachability order of selected triazines (propazine, terbuthylazine, sebuthylazine, ametryn, prometryn and terbutryn) in soil/sediment samples (organic carbon content ranging from 0.19 to 0.42%), analysing fractions collected from a soil packed microcolumn elution experiments. The procedure is fast, simple, highly sensitive and solvent free. SPME-GC-MS was also employed for the quantitative determination of triazines in the soil leachate, since the method showed good recovery yield. Detection limits were always better than 1 ng ml(-1). The method was tested on a contaminated landfill top soil. Prometryn and ametryn were identified through their MS spectra and then quantified. Terbuthylazine was used to assess recovery. Results compared well with those obtained by solvent extraction followed by HPLC-UV detection.     

Determination of pyrimethanil and kresoxim-methyl in soils by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A method using headspace solid-phase microextraction (HS-SPME) then gas chromatography–mass spectrometry with selected ion monitoring (GC–MS, SIM) has been developed for determination of trace amounts of the fungicides pyrimethanil and kresoxim-methyl in soil and humic materials. Both fungicides were extracted on to a fused-silica fibre coated with 85 m polyacrylate (PA). Response-surface methodology was used to optimise the experimental conditions. For soil samples the linear dynamic range of application was 0.004–1.000 g g^–1 for pyrimethanil and 0.013–1.000 g g^–1 for kresoxim-methyl. The detection limits were 0.001 g g^–1 and 0.004 g g^–1 for pyrimethanil and kresoxim-methyl, respectively. HP-SPME–GC–MS analysis was highly reproducible—relative standard deviations (RSD) were between 6.7 and 12.2%. The method was validated by analysis of spiked matrix samples and used to investigate the presence of pyrimethanil and kresoxim-methyl above the detection limits in soil and humic materials.     

Determination of isophorone in food samples by solid-phase microextraction coupled with gas chromatography-mass spectrometry

A simple and sensitive method for the determination of isophorone in food samples was developed by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Isophorone was separated within 10 min by GC-MS using a DB-1 capillary column and detected with selective ion monitoring mode. The HS-SPME using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber provided effective sample enrichment, and was carried out by fiber exposition at 60 degrees C for 45 min. The extracted isophorone was easily desorbed by fiber exposition in the injection port of a capillary GC-MS system, and carryover was not observed. Using this method, the calibration curve of isophorone was linear in the range 20-1000 pg/mL, with a correlation coefficient 0.9996 (n = 18), and the detection limit (S/N = 3) was 0.5 pg/mL. The HS-SPME/GC-MS method showed 25,000-fold higher sensitivity than the direct injection method (1 microL injection). The within-day and between-day precisions (relative standard deviations) at the concentration of 1 ng/mL isophorone were 3.9% and 6.1% (n=5), respectively. This method was successfully applied to the analysis of food samples without interference peaks. The recoveries of isophorone spiked into food sample were above 84% for a 50 or 500 pg/mL spiking concentration. The analytical results of the contents of isophorone in various food samples were presented.     

Determination of chloroanisole compounds in red wine by headspace solid-phase microextraction and gas chromatography-mass spectrometry

The objectives of this study, were the development and validation of an analytical method for the determination of 2,4,6-trichloroanisole (TCA), 2,3,4,6-tetrachloroanisole (TeCA) and pentachloroanisole (PCA) in red wine by headspace solid-phase microextraction and GC-MS as well as the application of the optimized and validated method for the quatification of chloroanisoles in different red wines from Navarra. To carry out this study, the extraction variables have been optimized. The fiber and the experimental design selected permit the determination of low analyte concentrations (ng/L) with good accuracy (<5%). Moreover, an analytical method for the determination of TCA and TeCA in wine by GC-MS has been validated. The results obtained in the validation step, recovery values, detection and quantitative limits, and precision were acceptable for all the analytes in the ranges of concentration studied (<5% and <10% for TCA and TeCA, respectively). This method has been used as an analytical method for the quantification of TCA and TeCA in red wine samples that were selected for this study, yielding good results.     

Fast determination of paeonol in plasma by headspace solid-phase microextraction followed by gas chromatography-mass spectrometry

Paeonol is the active component in the traditional Chinese medicines (TCMs), such as Cynanchum paniculatum, which has been used to treat many diseases, such as eczema. In this work, a simple, rapid and sensitive method was developed for the determination of paeonol in rabbit plasma, which was based on headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). The extraction parameters of fiber coating, sample temperature, extraction time, stirring rate and ion strength were systemically optimized; the method linearity, detection limit and precision were also investigated. It was shown that the proposed method provided a good linearity (0.02-20 μg mL⁻¹, R² > 0.990), low detection limit (2.0 ng mL⁻¹) and good precision (R.S.D. value less than 8%). Finally, GC/MS following HS-SPME was applied to fast determination of paeonol in rabbit plasma at different time point after oral demonstration of Cynanchum paniculatum essential oil. The experimental results suggest that the proposed method provided an alternative and novel approach to the pharmacokinetics study of paeonol in the TCMs.     

Determination of triazines in soil by microwave-assisted extraction followed by solid-phase microextraction and gas chromatography-mass spectrometry

A method for determining triazine herbicides in soil samples that combines microwave-assisted extraction with solid-phase microextraction is described. Water containing 1% methanol was employed as extractant. The parameters of solid-phase microextraction and microwave-assisted extraction were investigated. In solid-phase microextraction, particular attention was paid to the negative effect of salt on fiber stability. Our experiments showed that this effect could be effectively reduced by simply washing the fiber with deionized water. The selected triazines could be efficiently extracted by the aqueous extractant at 105 degrees C for 3 min, with 80% output of maximum power (1,200 W). The extraction procedure provided good precision (<7%) and recoveries (76.1-87.2%). The limits of detection were in the range 2-4 microg/kg. Compared with conventional liquid extraction, microwave-assisted extraction-solid-phase microextraction was more efficient, accurate and faster, and used a very small amount of organic solvent (only 250 microL methanol). The extraction of aged spiked soil samples indicated that, although the recoveries were lower than those of freshly spiked samples, they were nevertheless satisfactory for the quantitative analysis of real-world samples.     

Determination of volatile oak compounds in wine by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A headspace solid-phase microextraction (HS-SPME) and gas chromatography (GC) coupled to mass spectrometry (MS) method was developed to identify and quantify 14 volatile oak compounds in aged red wines. The most important HS-SPME variables were optimised by experimental design technique in order to improved the extraction process. The selected conditions were: 10 mL of sample in 20 mL sealed vials with addition of 30% of sodium chloride (saturated solution), divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS) fibre, 10 min of pre-incubation time, 70 degrees C of temperature and 60 min of extraction time without agitation. The features of the method were established for the studied compounds in terms of linear range, slope and intercept of the calibration graphs, detection and quantification limits and repeatability. For all compounds detection limits were below their threshold levels and repeatability, in terms of relative standard deviation, was good, with values between 3 and 11%. Finally, the method was applied to the analysis of six aged red wines by both internal standard and standard addition calibration methods. The concentrations obtained with both methods were statistically compared.     

顶空固相微萃取-气相色谱-质谱联用测定香水中5种合成麝香

建立了香水中5种合成麝香的顶空固相微萃取-气相色谱-质谱联用分析方法。实验选用65 μm的聚二甲基硅氧烷-二乙烯基苯(PDMS-DVB)萃取纤维,在磁力搅拌600 r/min条件下,考察了萃取温度、平衡时间、萃取时间、解吸时间、进样口温度和盐效应6个方面对实验结果的影响。优化后的条件为: 10 mL顶空瓶中加入适量用水稀释过的样品,于60 ℃平衡3 min后,顶空萃取20 min,随即插入气相色谱进样口,于250 ℃解吸3 min进行定性、定量分析。5种合成麝香在0.05～1.00 μg/g范围内线性关系良好,检出限(LOD)为0.6～2.1 ng/g。空白样品在3个浓度加标水平下(0.05, 0.50, 1.00 μg/g)的回收率为82.0%～103.3%,相对标准偏差(RSD)为1.8%～9.4%。本方法简便、准确、快速、灵敏,适用于香水中合成麝香的分析检验工作。     

Determination of pyrimethanil and kresoxim-methyl in green groceries by headspace solid-phase microextraction and gas chromatography-mass spectrometry

A method for determination of trace amounts of the fungicides pyrimethanil and kresoxim-methyl in green groceries, previous headspace solid-phase microextraction (HSSPME), was developed using gas chromatography-mass spectrometry and selected ion monitoring (GC-MS, SIM). Both fungicides were extracted with a fused-silica fiber coated with 85 microm polyacrylate. The effects of pH, ionic strength, extraction and desorption times as well as the extraction temperature were studied. The linear concentration range of application was 12.5-250 ng g(-1) for both compounds, with detection limits of 1.8-2.0 ng g(-1) for pyrimethanil and 2.8-3.1 ng g(-1) for kresoxim-methyl. SPME/GC-MS analysis yielded good reproducibility (RSD between 7.4 and 15.0%). It was applied to check the eventual existence of pyrimethanil and kresoxim-methyl above the detection limits on grapes, strawberries, tomatoes and ketchup samples. The method validation was completed with spiked matrix samples. It can be applied as a monitoring tool in grapes, strawberries, tomatoes and ketchup samples.