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.     

Physically incorporated extraction phase of solid-phase microextraction by sol-gel technology

A sol-gel method for the preparation of solid-phase microextraction (SPME) fiber was described and evaluated. The extraction phase of poly(dimethysiloxane) (PDMS) containing 3% vinyl group was physically incorporated into the sol-gel network without chemical bonding. The extraction phase itself is then partly crosslinked at 320 degrees C, forming an independent polymer network and can withstand desorption temperature of 290 degrees C. The headspace extraction of BTX by the fiber SPME was evaluated and the detection limit of o-xylene was down to 0.26 ng/l. Extraction and determination of organophosphorus pesticides (OPPs) in water, orange juice and red wine by the SPME-GC thermionic specified detector (TSD) was validated. Limits of detection of the method for OPPs were below 10 ng/l except methidathion. Relative standard deviations (RSDs) were in the range of 1-20% for pesticides being tested.     

Multiwalled Carbon Nanotube Coated on Stainless Steel Wire for Solid-Phase Microextraction of Organochlorine Pesticides in Water

A novel solid-phase microextraction (SPME) fiber was prepared by coating multiwalled carbon nanotube (MWCNTs) on a stainless steel wire, and its characteristics were studied. To evaluate the MWCNTs coating, the fiber was used for the extraction of some organochlorine pesticides (OCPs) from water samples by Headspace SPME (HS-SPME) mode. Potential factors affecting the extraction efficiency such as extraction time, extraction temperature, agitation, ionic strength, desorption temperature, and time were also optimized. Several experiments were carried out by water spiked with target compounds to evaluate the analytical characteristics of the proposed method under optimized conditions. The linearity was from 0.1 to 10 ug/L with the linear correlation coefficients (r) ranging from 0.9956 to 0.9995. The limits of detection (LOD, S/N = 3) for these pesticides were between 0.43 and 2.13 ng/L and the precision (RSD, n = 5) was 2.53–12.25%. When this method was applied for the spiked real river sample, the relative recoveries ranged from 72.4% to 134.7% for the tested OCPs.     

Methods for selective determination of persistent organochlorine pesticide residues in water and sediments by capillary gas chromatography and electron-capture detection

Different extraction methods were evaluated for the determination of fifteen organochlorine pesticides (OCPs) in water and sediments. Liquid-liquid extraction (LLE) was evaluated for the pesticides analyses in water while Soxhlet extraction (SE) and microwave assisted extraction (MAE) methods were compared in sediment. Of all the extracting solvents used, dichloromethane gave the best results. Percentage recoveries ranged from 71.03 +/- 8.15 (dieldrin) to 101.25 +/- 2.17% [a-benzenehexachloride (alpha-BHC)] in water with LLE. In sediments the percentage recoveries with Soxhlet extraction method varied between 88.22 +/- 7.85 (endrin) and 109.63 +/- 5.10% (beta-BHC) and ranged from 74.11 +/- 9.82 (2,4 DDT) to 97.50 +/- 4.56% (alpha-BHC) with MAE. The limits of detection for the OCPs ranged from 5.5 to 20.6 ng/l and between 0.6 and 2.1 ng/g. respectively. The LLE and the SE methods were applied to water and sediments samples, respectively, from marine and freshwater sources in the Eastern Cape Province of South Africa that receive runoffs from agricultural lands and effluents from industries. The levels of OCPs ranged from 5.5 (2,4-DDD) to 450 +/- 0.10 ng/l (beta-BHC) in water samples and from 0.6 (aldrin and 2,4-DDD) to 184 +/- 0.12 ng/g (beta-BHC) in sediments for triplicate analyses. Some endocrine disrupting OCPs such as DDT, DDE, heptachlor, endosulphan and the chlordanes were detected.     

Study on a novel circulating cooling solid-phase microextraction method

A novel solid-phase microextraction (SPME) setup, circulating cooling solid-phase microextraction (CC-SPME), is developed for determining organochlorine pesticides (OCPs) in water. The linearity area of this method is 0.5-120 microg/l, its RSD value is less than 10% and detection limit is in the low ng/l when it is used to detect gamma-hexachlorocyclohexane, which is better than traditional headspace SPME (HS-SPME) and direct immersion SPME (DI-SPME) methods. The influence of factors such as pH, ionic intensity, adsorption time, and adsorption temperature were also investigated, respectively.     

An efficient and fast microwave-assisted extraction method developed for the simultaneous determination of 18 organochlorine pesticides in sediment

An efficient and fast microwave-assisted extraction (MAE) method followed by gas chromatographic separation with mass spectrometric detection (GC–MS) was developed for the extraction of 18 organochlorine pesticides (OCPs) from sediment. Parameters affecting the MAE procedure such as the type and volume of the extraction solvent, irradiation power, temperature and irradiation time were successfully optimised. Under the optimal conditions, extraction efficiencies in the range of 73.4–119% were obtained with THF–HEX (9:1, v/v) for all OCPs studied. The method was linear over the range of 2.9–5000 ng g^?1 with determination coefficients (r²) higher than 0.992 for all analytes. The limits of detection, LODs (S/N = 3), obtained varied from 1.0 to 2.2 ng g^?1 and limits of quantification, LOQs (S/N = 10) were between 2.9 and 6.8 ng g^?1. The proposed method was successfully applied to the analysis of real sediment samples and acceptable recoveries from 70.1 to 124% with RSDs ≤14.8% were obtained. 10 OCPs were determined below their LOQ and 8 OCPs in the range of 124–2830 ng g^?1. The MAE method was compared with Soxhlet, shake flask and ultrasonic solvent extraction techniques. Thus, the MAE–GC–MS method could efficiently be used for selective extraction and quantification of the target analytes from the complex sediment matrices.     

Solid-phase microextraction for organochlorine pesticide residues analysis in Chinese herbal formulations

Solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC-MS) was used to determine pesticide residues in Chinese herbal formulations. Fibers coated with a 100-microm film thickness of poly(dimethylsiloxane) was used to extract 19 organochlorine pesticides (OCPs). The pesticides in the study consisted of alpha-, beta-, gamma-and delta-hexachlorocyclohexane, p,p'-DDD, p,p'-DDE, p,p'-DDT, o,p'-DDT, aldrin, dieldrin, endrin, endrin aldehyde, endrin ketone, endosulfan (I, II and sulfate), heptachlor, heptachlor epoxide, and methoxychlor. The optimal experimental procedures for the adsorption and desorption of pesticides were evaluated. The linearity was obtained with a precision below 11% RSD for the studied pesticides expect endosulfan sulfate (21%) in a wide range from 1 to 200 ng/g. Detection limits were reached at below ng/g levels. Heptachlor epoxide was determined at a calculated limit of 0.03 ng/g. Comparison between SPME and Soxhlet extraction showed that SPME has a less than one order detection limit for residue pesticide determination. The proposed method was tested by analyzing herbal formulations from a local market for OCP multiresidues. Some residues studied were detected in the analyzed samples. The results demonstrate the suitability of the SPME-GC-MS approach for the analysis of multi-residue OCPs in Chinese herbal formulations.     

Determination of 17 kinds of banned organochlorine pesticides in water by activated carbon fiber-solid phase microextraction coupled with GC-MS.

Activated carbon fiber (ACF) as extraction fiber for solid-phase microextraction (SPME) and its application for the analysis of banned organochlorine pesticides (OCPs) were investigated. Firstly, ACF was activated by different concentration of zinc chloride, which indicated that ACF activated by 60% zinc chloride had a reasonable specific surface area, pore volume and pore distribution. Secondly, the parameters for the ACF-SPME procedure, the adsorption and desorption conditions, were also optimized when coupled with gas chromatography-mass spectrometry (GC-MS). Thirdly, the ACF-SPME was used to analyze 17 kinds of OCPs in water. The linearity of most pesticides was found to be between 0.2 and 50 microg/l with GC-MS under the selected ion monitoring (SIM) acquisition mode. The limits of detection (LOD) at the sub microg/l were obtained. The work demonstrated here shows that ACF is a promising alternative for the SPME procedure.     

Evaluation of microwave-assisted extraction for the analysis of polychlorinated biphenyls and organochlorine pesticides in fish

The efficiency of microwave-assisted extraction (MAE) was evaluated for the analysis of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in fish. An isotope dilution method was used for quantification via analysis of the samples by gas chromatography and mass spectrometry. MAE solvent, temperature, and time were optimized, and observed concentrations were compared. The MAE results were also compared to those of other extraction techniques (Soxhlet extraction, pressurized liquid extraction, saponification, and homogenization). Concentrations of PCBs and OCPs obtained by MAE at 120 degrees C for 10 min were comparable to those by the other techniques. The results suggest that MAE can be used for the analysis of PCBs and OCPs in fish.     

原位溶剂热聚合法制备金属有机骨架/碳化氮纳米片涂覆的固相微萃取纤维用于红茶中农药残留的高灵敏检测

有机氯（OCPs）和拟除虫菊酯（PYs）是两类广泛使用的农药,对自然环境和人类健康具有极大危害。在本研究中,通过原位溶剂热聚合法制备了金属有机骨架/碳化氮纳米片（UiO-66/HOCN）复合材料涂覆的固相微萃取（SPME）纤维,该纤维拥有良好的稳定性,并对OCPs和PYs具有高效的萃取性能。将其与气相色谱-质谱（GC-MS）相结合,建立了用于OCPs和PYs检测的高灵敏分析方法。该方法对9种农药目标物表现出了令人满意的回收率和重现性,具有检出限低（0.03~0.30 ng/L）、线性范围宽（0.1~800.0 ng/L）和线性相关系数良好（≥ 0.9978）等优点。将所建立的方法用于实际红茶样品中农药残留的检测,成功地在实际样品中检测出了艾试剂（6.6 ng/L）、α-硫丹（54.7 ng/L）和联苯菊酯（185.8 ng/L）。实验结果表明,所建立的分析方法适用于复杂基质中农药残留的分析和监测。     

Development and application of polymer-coated hollow fiber membrane microextraction to the determination of organochlorine pesticides in water

A novel extraction procedure coupled with gas chromatography-mass spectrometric detection for quantification of organochlorine pesticides (OCPs) in water is described. Amphiphilic polyhydroxylated polyparaphenylene (PH-PPP) was synthesized and coated on the surfaces of a porous polypropylene hollow fiber membrane (HFM). Due to the high porosity of the HFM, maximum active surface area to achieve high extraction efficiency is expected. The polymer-coated HFM was used for the extraction of 15 OCPs from water. The extraction efficiency was compared with emerging and established methods such as liquid-phase microextraction (LPME), solid-phase microextraction (SPME) and stir bar sorptive extraction (SBSE) techniques. We term the current procedure as polymer-coated hollow fiber microextraction (PC-HFME). PC-HFME showed good selectivity and sensitivity. Detection limits for OCPs were in the range of 0.001-0.008 microg l(-1). The sensitivity and selectivity of the coated HFM could be adjusted by changing the characteristics of the coated PH-PPP film.     

羟基聚甲基苯基硅氧烷固相微萃取纤维的制备及在蔬菜中农药残留分析的应用

通过合成羟基聚甲基苯基硅氧烷(PMPS-OH)材料,制备固相微萃取(SPME)纤维涂层.通过与商品化聚二甲基硅氧烷(PDMS)、聚丙烯酸酯(PA)和PDMS/聚二乙烯基苯(DVB)纤维对六六六异构体(α,β,γ,δ-BHC)、DDT及其衍生物(p,p′-DDD,p,p′-DDE,o,p′-DDT,p,p′-DDT)、联苯菊酯、甲氰菊酯、高效氟氯氰菊酯、三氟氯氰菊酯、氯氰菊酯和氰戊菊酯等选定农药萃取效果的比较,所制备的PMPS-OH纤维具有更好的萃取效率.对SPME实验条件进行了研究和优化,测定方法对各种农药的线性范围多在0.01～2 ng/g之间,相应的检出限在0.001～0.05 ng/g范围,回收率在50.5%～103%.方法已被应用于蔬菜样品中农残的检测.     

Electrodeposited polyaniline as a fiber coating for solid-phase microextraction of organochlorine pesticides from water

The study on the performance of polyaniline as a fiber coating for solid-phase microextraction (SPME) purposes has been reported. Polyaniline coatings were directly electrodeposited on the surface of a stainless steel wire and applied for the extraction of some organochlorine pesticides (OCPs) from water samples. Analyses were performed using GC-electron capture detection (GC-ECD). The results obtained show that polyaniline fiber coating is suitable for the successful extraction of organochlorine compounds. This behavior is most probably due to the porous surface structure of polyaniline film, which provides large surface areas and allowed for high extraction efficiency. Experimental parameters such as adsorption and desorption conditions were studied and optimized. The optimized method has an acceptable linearity, with a concentration range of 1-5000 ng/L. Single fiber repeatability and fiber-to-fiber reproducibility were less than 12 and 17%, respectively. High environmental resistance and lower cost are among the advantages of polyaniline fibers over commercially available SPME fibers. The developed method was applied to the analysis of real water samples from Yangtse River and Tianmu Lake.     

A novel graphene nanosheets coated stainless steel fiber for microwave assisted headspace solid phase microextraction of organochlorine pesticides in aqueous samples followed by gas chromatography with electron capture detection

In this study, a novel graphene nanosheets (GNSs) coated solid phase microextraction (SPME) fiber was prepared by immobilizing microwave synthesized GNSs on a stainless steel wire. Microwave synthesized GNSs were verified by X-ray diffraction, field emission-scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM). GNS-SPME fiber was characterized using FE-SEM and the results showed the GNS coating was homogeneous, porous, and highly adherent to the surface of the stainless steel fiber. The performance and feasibility of the GNS-SPME fiber was evaluated under one-step microwave assisted (MA) headspace (HS) SPME followed by gas chromatography with electron capture detection for five organochlorine pesticides (OCPs) in aqueous samples. Parameters influencing the extraction efficiency of MA-HS-GNS-SPME such as microwave irradiation power and time, pH, ionic strength, and desorption conditions were thoroughly examined. Under the optimized conditions, detection limits for the OCPs varied between 0.16 and 0.93 ng L(-1) and linear ranges varied between 1 and 1500 n gL(-1), with correlation coefficients ranging from 0.9984 to 0.9998, and RSDs in the range of 3.6-15.8% (n=5). In comparison with the commercial 100 μm polydimethylsiloxane fiber, the GNS coated fiber showed better extraction efficiency, higher mechanical and thermal stability (up to 290°C), longer life span (over 250 times), and lower production cost. The method was successfully applied to the analysis of real water samples with recoveries ranged between 80.1 and 101.1% for river water samples. The results demonstrated that the developed MA-HS-GNS-SPME method was a simple, rapid, efficient pretreatment and environmentally friendly procedure for the analysis of OCPs in aqueous samples.     

An expeditious method for the determination of organochlorine pesticides residues in estuarine sediments using microwave assisted pre-extraction and automated headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry

Determination of organochlorine pesticides (OCPs) in sediments implicates extraction of these compounds from the matrix, which is difficult owing to strong interaction among OCPs and different constituents of the sediments, particularly organic content. The method here described is a combination of microwave assisted extraction (MAE), headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS), acting in selected-ion storage mode, or GC-electron capture detector (ECD, for routine analysis). Methanol was used as extracting solvent and aliquots of the MAE extracts (after inclusion of a step for sulfur elimination when required) were used to prepare aqueous solutions for HS-SPME. A complete automation of the SPME procedure increases the sample throughput, including standard addition for calibration purpose. The procedure has the advantage of exclude additional clean-up steps and pre-concentration before SPME. Application to reference sediments of different characteristics revealed absence of significant interferences from the matrix for alpha-lindane, gamma-lindane, aldrin, dieldrin, endrin, 4,4'-DDT, 4,4'-DDD, 4,4'-DDE, heptachlor, heptachlor epoxide and good sensitivity. Detection limits ranged from 0.005 to 0.11 ng of OCP per gram of dried sediment using GC-MS and from 0.01 to 0.26 ngg(-1) using GC-ECD. The linear response ranges embraced 5-6 orders of magnitude (up to 1000 ngg(-1)) in GC-MS, being narrower for GC-ECD. The method was successfully applied to sandy and muddy sediments from Portuguese rivers estuaries, enabling quantification of seven OCPs. The method resulted effective, relatively simple and fast, being suitable for routine monitoring of residues of OCPs from sediments of different grain size and organic matter content, which influence concentration, mobility and availability of contaminants.     

Novel fiber coated with β-cyclodextrin derivatives used for headspace solid-phase microextraction of ephedrine and methamphetamine in human urine

Heptakis (2,6-di-O-methyl)-β-cyclodextrin (DM-β-CD) blending with hydroxy-terminated silicone oil (OH-TSO) coated solid-phase microextraction (SPME) fiber (DM-β-CD/OH-TSO) was first prepared with sol-gel technology and applied to headspace SPME for analysis of ephedrine (EP) and methamphetamine (MA) in human urine by gas chromatography (GC). By exploiting the advantages of the unique cavity-shaped cyclic molecular structure of CD and the superiorities of sol-gel coating technique, the novel fiber showed desirable extraction ability and operational stability. Influence of relevant experimental parameters (extraction time, extraction temperature, basicity, ionic strength, etc.) was systematically investigated. In the optimal conditions the proposed headspace SPME-GC method provided good linearity over four orders of magnitude with limit of detection (LOD) of ng/ml (0.33 ng/ml for EP, 0.60 ng/ml for MA). The recoveries of EP and MA in urine were 98.0% and 98.2%. And the relative standard deviations (R.S.D., n = 6) for EP and MA were 3.9% and 5.0%, respectively.     

Microwave-assisted steam distillation for the determination of organochlorine pesticides and pyrethroids in Chinese teas

In this work, microwave-assisted steam distillation (MASD) extraction method followed by gas chromatography/electron capture detection (GC/ECD) was developed for the determination of organochlorine pesticides (OCPs) and pyrethroids in the Chinese teas. MASD is a combination of microwave-assisted extraction (MAE) and steam distillation techniques. Water vapor generated by microwave irradiation is used to accelerate desorption of the analytes from the sample, and the nonpolar organic solvent used for trapping the analytes is kept from direct contact with the sample by the water. Therefore, relatively clean extracts were obtained compared to the method directly using organic solvent as extraction solvent, such as ultrasonic extraction (USE). Microwave power of 200 W and irradiation time of 2 min was found to be the optimum conditions for the MASD process, and n-heptane was chosen as the analyte-trapping solvent in the study. Five OCPs (α-HCH, γ-HCH, dicofol, p,p′-DDE, p,p′-DDT) and two pyrethroids (bifenthrin, fenvalate) were determined using this extraction method in the tea samples. The relative standard deviation (R.S.D.) of the analytes varied from 2.2 to 8.4%, and the method detection limits (MDLs) found were lower than 0.23 μg/kg. The recoveries of the seven compounds in the Jasmine tea sample were between 84.04 and 110.1%. Comparative results obtained by MASD and USE were also discussed in the study.     

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%.     

A novel headspace solid-phase microextraction method for the exact determination of organochlorine pesticides in environmental soil samples

A novel method of determining organochlorine pesticides (OCPs) is described. It is based on solid-phase microextraction (SPME) and gas chromatography–electron capture detection. During the development of the method, soil samples were prepared, spiked with standard solution, and then aged for some time. Extraction conditions such as the extraction time, the NaCl content, the volume of water, the extraction temperature and the desorption time were investigated and optimized. The limits of detection obtained using the method ranged from 0.10 to 0.51 ng g⁻¹, and relative standard deviations were lower than 10% for most organochlorine pesticides. Real soil samples were successfully analyzed using the proposed method. The results from the method developed here were in good agreement with those obtained using ultrasonic extraction. The result demonstrates that aging soils spiked with standard solution is an important method development step, because the soil samples obtained using this approach are more like real soils than those obtained when aging is not used.      

Determination of organochlorine pesticides and their metabolites in soil samples using headspace solid-phase microextraction

An analytical procedure was developed using headspace solid-phase microextraction (HS-SPME) for the determination of organochlorine pesticides (OCPs) and their metabolites in sandy soil samples. The developed procedures involving fiber selection, temperature effect, absorption time, soil matrix and the addition of solvents of different polarity were optimized. Also, the results were compared to those achieved using Soxhlet extraction standard method. The 100-microm polydimethylsiloxane (PDMS) and 65-microm PDMS-divinylbenzene showed good extraction efficiency for 18 organochlorine pesticides. An increase in the extraction efficiency of organochlorine pesticides and the metabolites was observed when the temperature increased, and an optimum temperature of 70 degrees C for extracting OCPs was obtained. The application of other hydrophilic solvents had different effects on the extraction of organochlorine pesticides and the metabolites. Higher responses of OCPs were obtained when 5 ml of water was added to the soil. Good linearity of OCPs between 0.2 and 4 ng/g soil was observed. The relative standard deviation was found to be lower than 25%. Also the limits of detection were between 0.06 and 0.65 ng/g, which were lower than those obtained using Soxhlet extraction. Moreover, the optimized HS-SPME procedure was applied to the analysis of OCPs in certified reference material (CRM) 804-050 soil and compared with Soxhlet extraction procedure. Results obtained in this study were in good agreement with those obtained using Soxhlet extraction. The mean values obtained using HS-SPME technique were in the range of 16.5 to 1459.6 mg/kg, which corresponds to the recoveries of 68% to 127% of the certified values of CRM soil.