Solid-phase microextraction–gas chromatographic determination of volatile monoaromatic hydrocarbons in soil

Benzene, toluene, ethylbenzene, three isomers of xylene, and cumene have been isolated and enriched from soil samples by a combination of water extraction at room and elevated temperature and headspace–solid-phase microextraction before their gas chromatographic–mass spectrometric (GC–MS) determination. The conditions used for all stages of sample preparation and chromatographic analysis were optimized. Analytes sampled on a polydimethylsiloxane-coated solid-phase microextraction fiber were thermally desorbed in the split/splitless injector of a gas chromatograph (GC) coupled with a mass spectrometer (MS). The desorption temperature was optimized. The GC separation was performed in a capillary column. Detection limits were found to be of the order of ca. 1 ng g^–1. Relative recoveries of the analytes from soils were found to be highly dependent on soil organic-matter content and on compound identity; they ranged from ca 92 to 96% for sandy soil (extraction at room temperature) and from ca 27 to 55% for peaty soil (extraction at elevated temperature). A few real-world soil samples were analyzed; the individual monoaromatic hydrocarbon content ranged from below detection limits to 6.4 ng g^–1 for benzene and 8.1 for the total of p- + m-xylene.     

Accelerated solvent extraction combined with dispersive liquid–liquid microextraction before gas chromatography with mass spectrometry for the sensitive determination of phenols in soil samples

A method combining accelerated solvent extraction with dispersive liquid–liquid microextraction was developed for the first time as a sample pretreatment for the rapid analysis of phenols (including phenol, m‐cresol, 2,4‐dichlorophenol, and 2,4,6‐trichlorophenol) in soil samples. In the accelerated solvent extraction procedure, water was used as an extraction solvent, and phenols were extracted from soil samples into water. The dispersive liquid–liquid microextraction technique was then performed on the obtained aqueous solution. Important accelerated solvent extraction and dispersive liquid–liquid microextraction parameters were investigated and optimized. Under optimized conditions, the new method provided wide linearity (6.1–3080 ng/g), low limits of detection (0.06–1.83 ng/g), and excellent reproducibility (<10%) for phenols. Four real soil samples were analyzed by the proposed method to assess its applicability. Experimental results showed that the soil samples were free of our target compounds, and average recoveries were in the range of 87.9–110%. These findings indicate that accelerated solvent extraction with dispersive liquid–liquid microextraction as a sample pretreatment procedure coupled with gas chromatography and mass spectrometry is an excellent method for the rapid analysis of trace levels of phenols in environmental soil samples.     

Analysis of benzene, toluene, ethylbenzene, xylenes and n-aldehydes in melted snow water via solid-phase dynamic extraction combined with gas chromatography/mass spectrometry

The present study describes a method based on headspace-solid-phase dynamic extraction (HS-SPDE) followed by GC/MS for the qualitative and quantitative analysis of benzene, toluene, ethylbenzene, o-, m- and p-xylene (BTEX), and n-aldehydes (C(6)-C(10)) in water. To enhance the extraction capability of the HS-SPDE a new cooling device was tested that controls the temperature of the SPDE needle during extraction. Extraction and desorption parameters such as the number of extraction cycles, extraction temperature, desorption volume and desorption flow rate have been optimized. Detection limits for BTEX ranged from 19 ng/L (benzene) to 30 ng/L (m/p-xylene), while those for n-aldehydes ranged from 21 ng/L (n-heptanal) to 63 ng/L (n-hexanal). At a concentration level of 2 microg/L, the relative standard deviations (RSDs) for BTEX ranged from 3.9% (benzene) to 15.3% (ethylbenzene), while RSDs for n-aldehydes were between 6.1% (n-octanal) and 16.5% (n-hexanal) (n=7). Best results were obtained when the analyzed water samples were heated to 50 degrees C. At a water temperature of 70 degrees C GC responses decreased for all analyzed compounds. At a defined water temperature, a significant improvement of the GC response was achieved by cooling of the SPDE fiber during water extraction in comparison to an extraction keeping the fiber at room temperature. Evaluating the extraction cycles, for BTEX, the sensitivity was almost similar using 20, 40 and 60 extraction cycles. In contrast, the highest GC responses for n-aldehydes were achieved by the use of 60 extraction cycles. Optimizing the desorption parameters, best results were achieved using the smallest technical available desorption volume of 500 microL and the highest technical desorption flow rate of 50 microL/s. The method was applied to the analysis of melted snow samples taken from the Jungfraujoch, Switzerland (3580 m asl), revealing the presence of BTEX and aldehydes in snow.     

Application of ceramic/carbon composite as a novel coating for solid-phase microextraction

A ceramic/carbon composite was developed and applied as a novel coating for solid-phase microextraction (SPME). The ceramic/carbon coating exhibited several good properties for SPME, such as high extraction quantities and enhanced thermal and organic solvent stability. Under scanning electron microscopy (SEM), the tightly attached coating layer on stainless steel wire revealed excellent mechanical characteristics. Single fiber and fiber-to-fiber reproducibility were less than 6.9 and 9.5%, respectively. The effects of extraction and desorption parameters such as extraction time, stirring rate, ionic strength, and desorption temperature and desorption time on the extraction/desorption efficiency were investigated and optimized. Coupled to gas chromatography with a flame thermionic detector, the optimized SPME method was applied to the analysis of organophosphorus pesticides (OPPs) in aqueous samples. The calibration curves were linear from 0.05 to 200 ng mL(-1) for fenchlorphos, pirimiphos-methyl, chlorpyrifos, ethion and from 0.2 to 200 ng mL(-1) for quinalphos, and the limits of detection were between 5.2 and 34.6 ng L(-1). The recovery of the OPPs spiked in real water samples at 5 ng mL(-1) ranged from 86.2 to 103.4% and the relative standard deviations were less than 8.5%.     

Determination of organophosphorus pesticides in soil by headspace solid-phase microextraction

Headspace solid-phase microextraction (SPME) has been developed for the analysis of common organophosphorus pesticides in soil. Factors such as adsorption-time, sampling temperature and matrix modification by addition of water were carefully considered to optimize the extraction efficiency. This technique could achieve limits of detection of 143 ng/g for Malathion and Parathion, and 28.6 ng/g for Phorate, Diazinon and Disulfoton in humic soil when the extracted sample was analyzed by gas chromatography-flame ionization detector (GC-FID). Lower limits of detection of 28.6 ng/g for Malathion and Parathion, and 14.3 ng/g for Phorate, Diazinon and Disulfoton can be achieved by analyzing the extracted sample with gas chromatography/mass spectrometric detector (GC/MS). As the extraction efficiency was generally better when analyzing sandy soil, the limits of detection are envisaged to be even better for such a matrix. The technique was found to be reliable with good precision of about 6.5% RSD for the sandy soil and about 15% for the humic material. The poorer precision of extraction from the humic material is probably related to the poorer homogeneity of this material. The linearity of extraction was good with linear calibration in the range of 0.143 to 28.6 μg/g. Finally, headspace SPME was compared to aqueous extraction of soil followed by SPME (LE-SPME). The recoveries obtained by headspace SPME were comparable to those from liquid-liquid extraction of soil followed by SPME. However, the analysis of headspace SPME has less background interference. Perhaps, the greatest advantage of this technique is its non-destructive nature so that it is possible to perform further laboratory analysis of the samples after headspace SPME has been carried out. Received: 13 July 1998 / Revised: 10 November 1998 / Accepted: 17 November 1998     

Determination of organophosphorus pesticides in soil by headspace solid-phase microextraction

Headspace solid-phase microextraction (SPME) has been developed for the analysis of common organophosphorus pesticides in soil. Factors such as adsorption-time, sampling temperature and matrix modification by addition of water were carefully considered to optimize the extraction efficiency. This technique could achieve limits of detection of 143 ng/g for Malathion and Parathion, and 28.6 ng/g for Phorate, Diazinon and Disulfoton in humic soil when the extracted sample was analyzed by gas chromatography-flame ionization detector (GC-FID). Lower limits of detection of 28.6 ng/g for Malathion and Parathion, and 14.3 ng/g for Phorate, Diazinon and Disulfoton can be achieved by analyzing the extracted sample with gas chromatography/mass spectrometric detector (GC/MS). As the extraction efficiency was generally better when analyzing sandy soil, the limits of detection are envisaged to be even better for such a matrix. The technique was found to be reliable with good precision of about 6.5% RSD for the sandy soil and about 15% for the humic material. The poorer precision of extraction from the humic material is probably related to the poorer homogeneity of this material. The linearity of extraction was good with linear calibration in the range of 0.143 to 28.6 μg/g. Finally, headspace SPME was compared to aqueous extraction of soil followed by SPME (LE-SPME). The recoveries obtained by headspace SPME were comparable to those from liquid-liquid extraction of soil followed by SPME. However, the analysis of headspace SPME has less background interference. Perhaps, the greatest advantage of this technique is its non-destructive nature so that it is possible to perform further laboratory analysis of the samples after headspace SPME has been carried out.     

Solid-phase microextraction with on-fiber derivatization for the analysis of anti-inflammatory drugs in water samples

A sensitive and solvent-free procedure for the determination of non-steroidal acidic anti-inflammatory drugs in water samples was optimized using solid-phase microextraction (SPME) followed by on-fiber silylation of the acidic compounds and gas chromatography-mass spectrometry (GC-MS) determination. Microextraction was carried out directly over the filtered water samples using a polyacrylate fiber. Derivatization was performed placing the SPME fiber, loaded with the extracted analytes, in the headspace of a vial containing 50 microl of N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA). Derivatives were desorbed for 3 min in the GC injector. Influence of several parameters in the efficiency of microextraction (volume of sample, time, pH, type of fiber coating, etc.) and derivatization steps (time, temperature and volume of MTBSTFA) was systematically investigated. In the optimal conditions an excellent linearity over three orders of magnitude and quantification limits at the ng/l level (from 12 to 40 ng/l) were achieved. The proposed method was applied to the determination of acidic compounds in sewage water and results compared to those obtained using solid-phase extraction (SPE) followed by the derivatization of the compounds in the organic extract of the solid-phase extraction cartridge.     

Determination of pyrethroid,organophosphate and organochlorine pesticides in water by headspace solid-phase microextraction

Simultaneous determination of pyrethroid, organophosphate (OP) and organochlorine (OC) pesticides in water was achieved with headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-electron-capture detection (GC-ECD). The parameters affecting HS-SPME of pesticides from water were optimized, including extraction temperature, sample and headspace volumes, and sodium chloride amounts. The effects of desorption temperature, desorption time, and position of the fibre in the GC inlet were also investigated. Extraction temperature was the most important factor affecting the recoveries of analytes, and the optimized temperature was 96°C. The addition of salt did not increase extraction efficiencies of the pesticides from the water. The optimized desorption conditions in the GC were as follows: desorption time of 10?min; desorption temperature of 260°C; and a 2?cm position of the fibre in the inlet. The method detection limits were in the low-ng/L level with a linearity range of 50–1000?ng/L for the OCs, 50–5000?ng/L for the OP, and 50–20?000?ng/L for the pyrethroids. These data demonstrated that HS-SPME is a sensitive method for the determination of pyrethroid, OC, and OP pesticides in water.     

Gas chromatography/ion trap mass spectrometry applied for the determination of polybrominated diphenyl ethers in soil

A gas chromatography/ion trap mass spectrometry (GC/ITMS) method was developed for the determination of polybrominated diphenyl ethers (PBDEs). ITMS parameters were optimized in order to achieve the best sensitivity for the PBDE analysis. Tandem mass spectrometry, along with an isotope dilution internal standard method, was used for the quantitation. Chromatographic windows were developed for mono- to hepta-BDEs, depending on the retention times when a 30-m GC column was used. A different 15-m column was used to analyze deca-BDE. Environmental soil samples collected from an electronic waste recycling site were prepared by using Soxhlet extraction and column chromatographic cleanup. Average recoveries of 61-118% were obtained for the 13C-labeled PBDE internal standards spiked in the samples prior to sample preparation. The accuracy represented by relative analytical errors was -24% to 18%, and the precision (relative standard deviation) was 11-26% (n=8). The method detection limits ranged from 0.013-0.25 ng/g for the PBDEs in soil.     

Application of head-space solid-phase microextraction coupled to comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry for the determination of multiple pesticide residues in tea samples

A new method has been developed to detect 36 pesticides that may contaminate tea samples (green, black and fruit tea). The hyphenation of solid-phase microextraction in head-space mode with a comprehensive two-dimensional gas chromatography coupled with high-speed time-of-flight mass spectrometry (HS-SPME-GC × GC/TOF MS) proved to be a quick alternative to conventional GC/MS methodology which employs solvent-based extraction. The key parameters for controlling HS-SPME performance were optimized, including fiber coating type, temperature and absorption time settings and tea matrix modification by adding water. Quantification was carried out using matrix-matched calibration. The repeatability of measurements, expressed as relative standard deviation (R.S.D.), was less than 24% for all analytes. The limits of quantification ranged from 1 to 28 μg kg⁻¹. The optimized method was applied to analyze real life samples obtained from a retail market. Results generated by the new SPME procedure and those obtained by using a conventional one involving ethyl acetate extraction and high-performance gel permeation chromatography (HPGPC) clean up agreed with each other for positive (containing residue) samples.     

超声辅助乳化液液微萃取-气相色谱-质谱分析水中的人工合成麝香

将超声辅助乳化与液液微萃取技术结合,建立了水体中人工合成麝香的气相色谱-质谱分析方法.优化前处理条件,包括萃取剂、萃取剂体积、萃取时间、萃取温度及离子强度的选择.结果表明:在10 mL水样中,加入50 μL氯苯作为萃取剂,4 0 MHz超声10 min,混匀,以4000 r/min离心10 min,移取下层有机相进样分析,效果佳.样品的富集倍数可达200倍,8种人工合成麝香在0.005～0.4 μg/L范围内线性关系良好,相关系数均大于0.994;检出限为0.3～0.5 ng/L;水样中加标回收率为96.2％～102.9％;相对标准偏差为2.3％～4.1％.本方法灵敏、快速、准确,可满足环境水样中痕量人工合成麝香监测的质控要求.     

Magnetic solid‐phase extraction or dispersive liquid–liquid microextraction for pyrethroid determination in environmental samples

The determination of 15 pyrethroids in soil and water samples was carried out by gas chromatography with mass spectrometry. Compounds were extracted from the soil samples (4 g) using solid–liquid extraction and then salting‐out assisted liquid–liquid extraction. The acetonitrile phase obtained (0.8 mL) was used as a dispersant solvent, to which 75 μL of chloroform was added as an extractant solvent, submitting the mixture to dispersive liquid–liquid microextraction. For the analysis of water samples (40 mL), magnetic solid‐phase extraction was performed using nanocomposites of magnetic nanoparticles and multiwalled carbon nanotubes as sorbent material (10 mg). The mixture was shaken for 45 min at room temperature before separation with a magnet and desorption with 3 mL of acetone using ultrasounds for 5 min. The solvent was evaporated and reconstituted with 100 μL acetonitrile before injection. Matrix‐matched calibration is recommended for quantification of soil samples, while water samples can be quantified by standards calibration. The limits of detection were in the range of 0.03–0.5 ng/g (soil) and 0.09–0.24 ng/mL (water), depending on the analyte. The analyzed environmental samples did not contain the studied pyrethroids, at least above the corresponding limits of detection.     

Polyvinylimidazole/sol–gel composite as a novel solid‐phase microextraction coating for the determination of halogenated benzenes from aqueous solutions

A polyvinylimidazole/sol–gel composite is proposed as a novel solid‐phase microextraction fiber to extract five halobenzenes from the headspace of aqueous solutions in combination with gas chromatography with mass spectrometry. The prepared fiber was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The obtained results showed that porous polyvinylimidazole/sol–gel composite was chemically deposited on fused silica fiber. The effect of important extraction parameters including extraction temperature, extraction time, and salt content were investigated. The optimum conditions were as follows: extraction temperature 25°C, extraction time 20 min, and salt concentration 30 w/v%. Detection limits and relative standard deviations of the developed method for halogenated benzenes were below 0.1 pg/mL and 15%, respectively. Repeatability of the proposed method, explained by relative standard deviation, varied between 5.48 and 9.15% (n = 5). The limits of detection (S/N = 3) ranged between 0.01 and 0.10 ng/L using gas chromatography with mass spectrometry with selected ion monitoring mode. For real sample analysis, three types of water samples with different matrices (ground, surface, and tap water) were studied. The optimized procedure was applied to extraction and method validation of halogenated benzenes in spiked water samples.     

Development and validation of a novel method for the analysis of chlorinated pesticides in soils using microwave-assisted extraction–headspace solid phase microextraction and gas chromatography–tandem mass spectrometry

A new procedure for determining eleven organochlorine pesticides in soils using microwave-assisted extraction (MAE) and headspace solid phase microextraction (HS-SPME) is described. The studied pesticides consisted of mirex, α- and γ-chlordane, p,p′-DDT, heptachlor, heptachlor epoxide isomer A, γ-hexachlorocyclohexane, dieldrin, endrin, aldrine and hexachlorobenzene. The HS-SPME was optimized for the most important parameters such as extraction time, sample volume and temperature. The present analytical procedure requires a reduced volume of organic solvents and avoids the need for extract clean-up steps. For optimized conditions the limits of detection for the method ranged from 0.02 to 3.6 ng/g, intermediate precision ranged from 14 to 36% (as CV%), and the recovery from 8 up to 51%. The proposed methodology can be used in the rapid screening of soil for the presence of the selected pesticides, and was applied to landfill soil samples.     

Dispersive solid‐phase extraction followed by vortex‐assisted dispersive liquid–liquid microextraction based on the solidification of a floating organic droplet for the determination of benzoylurea insecticides in soil and sewage sludge

A novel dispersive solid‐phase extraction combined with vortex‐assisted dispersive liquid–liquid microextraction based on solidification of floating organic droplet was developed for the determination of eight benzoylurea insecticides in soil and sewage sludge samples before high‐performance liquid chromatography with ultraviolet detection. The analytes were first extracted from the soil and sludge samples into acetone under optimized pretreatment conditions. Clean‐up of the extract was conducted by dispersive solid‐phase extraction using activated carbon as the sorbent. The vortex‐assisted dispersive liquid–liquid microextraction based on solidification of floating organic droplet procedure was performed by using 1‐undecanol with lower density than water as the extraction solvent, and the acetone contained in the solution also acted as dispersive solvent. Under the optimum conditions, the linearity of the method was in the range 2–500 ng/g with correlation coefficients (r) of 0.9993–0.9999. The limits of detection were in the range of 0.08–0.56 ng/g. The relative standard deviations varied from 2.16 to 6.26% (n = 5). The enrichment factors ranged from 104 to 118. The extraction recoveries ranged from 81.05 to 97.82% for all of the analytes. The good performance has demonstrated that the proposed methodology has a strong potential for application in the multiresidue analysis of complex matrices.     

Determination of organophosphorous pesticides in water using in-syringe ultrasound-assisted emulsification and gas chromatography with electron-capture detection

An in-syringe ultrasound-assisted emulsification microextraction (USAEME) was developed for the extraction of organophosphorus pesticides (OPPs) from water samples. The OPPs subsequently analyzed gas chromatography (GC) using a microelectron capture detector (μECD). Ultrasound radiation was applied to accelerate the emulsification of μL-level low-density organic solvent in aqueous solutions to enhance the microextraction efficiency of OPPs in the sample preparation for GC-μECD. Parameters affecting the efficiency of USAEME, such as the extraction solvent, solvent volume, pH, salt-addition, and extraction time were thoroughly investigated. Based on experimental results, OPPs were extracted from a 5 mL aqueous sample by the addition of 20 μL toluene as the extraction solvent, followed by ultrasonication for 30 s, and then centrifugation for 3 min at 3200 rpm, offered the best extraction efficiency. Detections were linear in the concentration of 0.01–1 μg/L with detection limits between 1 ng/L and 2 ng/L for OPPs. Enrichment factors ranged from 330 to 699. Three spiked aqueous samples were analyzed, and recovery ranged from 90.1% to 104.7% for farm-field water, and 90.1% to 101.8% for industrial wastewater. The proposed method provides a simple, rapid, sensitive, inexpensive, and eco-friendly process for determining OPPs in water samples.     

Au nanoparticles as a novel coating for solid-phase microextraction

A novel solid-phase microextraction fiber based on a stainless steel wire coated with Au nanoparticles was prepared and has been applied, coupled with gas chromatography, to the extraction of aromatic hydrophobic organic chemical pollutants in rainwater and soil extract. The solid-phase microextraction fiber exhibited excellent extraction efficiency and selectivity. Effects of extraction time, extraction temperature, ionic strength, stirring rate and desorption conditions were investigated and optimized. Single fiber repeatability and fiber-to-fiber reproducibility were less than 7.90% and 26.40%, respectively. The calibration curves were linear in a wide range for all analytes. Correlation coefficients ranged from 0.9941 to 0.9993. The as-established SPME-GC method was used successfully to two real natural samples. Recovery of analytes spiked at 10 μg L(-1) and 100 μg L(-1) ranged from 78.4% to 119.9% and the relative standard deviations were less than 11.3%.     

Single-drop microextraction and gas chromatography/mass spectrometric determination of anisaldehyde isomers in human urine and blood serum

The application of single-drop microextraction (SDME) followed by gas chromatography/chemical ionization mass spectrometry (GC/CI-MS) was investigated for the determination of anisaldehyde isomers in human urine and blood serum. The effects of extraction solvent, sample agitation rate, salt addition, sampling time and temperature on the extraction efficiency were examined and optimized. Analytical parameters such as linearity, reproducibility, detection limit and relative recovery were evaluated under the optimized experimental conditions. Good reproducibilities of replicate extractions (n = 5) were obtained, with relative standard deviation (RSD) values below 6%. The limits of detection (LOD) using an extraction time of 5 min were found to be in the range 2-5 ng/mL under the selected ion monitoring (SIM) mode of GC/MS. Recoveries of 82-98% were achieved after 5 min extraction.     

Determination of three antidepressants in urine using simultaneous derivatization and temperature‐assisted dispersive liquid–liquid microextraction followed by gas chromatography–flame ionization detection

This paper presents a fast and simple method for the extraction, preconcentration and determination of fluvoxamine, nortriptyline and maprotiline in urine using simultaneous derivatization and temperature‐assisted dispersive liquid–liquid microextraction (TA‐DLLME) followed by gas chromatography–flame ionization detection (GC‐FID). An appropriate mixture of dimethylformamide (disperser solvent), 1,1,2,2‐tetrachloroethane (extraction solvent) and acetic anhydride (derivatization agent) was rapidly injected into the heated sample. Then the solution was cooled to room temperature and cloudy solution formed was centrifuged. Finally a portion of the sedimented phase was injected into the GC‐FID. The effect of several factors affecting the performance of the method, including the selection of suitable extraction and disperser solvents and their volumes, volume of derivatization agent, temperature, salt addition, pH and centrifugation time and speed were investigated and optimized. Figures of merit of the proposed method, such as linearity (r² > 0.993), enrichment factors (820–1070), limits of detection (2–4 ng mL^?1) and quantification (8–12 ng mL^?1), and relative standard deviations (3–6%) for both intraday and interday precisions (concentration = 50 ng mL^?1) were satisfactory for determination of the selected antidepressants. Finally the method was successfully applied to determine the target pharmaceuticals in urine. Copyright © 2014 John Wiley & Sons, Ltd.     

全二维气相色谱-飞行时间质谱测定地下水中低环多环芳烃及其衍生物

建立了地下水中低环多环芳烃及其衍生物的全二维气相色谱-飞行时间质谱(GC×GC-TOF MS)检测方法。对比研究了液液萃取(LLE)和固相萃取(SPE)对地下水中低环多环芳烃及其衍生物的提取效率,优选液液萃取为前处理方法。在优化条件下,除1,2,3,4-四氢萘(r=0.987 2)和联苯(r=0.989 9)外,其它目标物在0.1~1 000μg/L范围内具有良好的线性关系,相关系数(r)均大于0.99。地下水的平均加标回收率为63.3%~111%,除喹啉的相对标准偏差(RSD,n=6)为24.9%外,其余目标物的RSD均小于9.5%,方法检出限在1.63~14.7 ng/L之间。该方法用于河北地区6个地下水样中低环多环芳烃及其衍生物的检测,4个样品有检出,最高浓度达353 ng/L。