Single-walled carbon nanotubes coated fibers for solid-phase microextraction and gas chromatography-mass spectrometric determination of pesticides in Tea samples

Using a single-walled carbon nanotubes (SWCNTs) as stationary phase of solid-phase microextraction (SPME) fibers, a simple, low cost and environmentally friendly method for extraction of 13 pesticides in Tea samples has been developed following gas chromatography-mass spectrometric determination. Potential factors affecting the extraction efficiency were investigated and optimized, including extraction and desorption time, extraction temperature, stirring rate, solution pH and ionic strength. Under optimized conditions, the linearity of the developed method was in the range of 0.125-25 ng/mL with correlation coefficients greater than 0.9928 and the limits of detections (LODs) were 0.027-0.23 ng/mL (S/N = 3). Meanwhile, the relative standard deviations (RSDs) for five successive measurements with single fiber, fiber-to-fiber, day-to-day were 2.3-13.0, 8.2-14.6 and 4.1-12.5%, respectively, indicating good reproducibility of the proposed method. The fiber had high extraction efficiency for studied pesticides in comparison with commercial poly(dimethylsiloxane) (PDMS) and polyacrylate (PA) fibers and could be used for more than 70 times without decrease of efficiency. The developed method was successfully applied for the analysis of real samples including green Tea, oolong Tea, white Tea, and flower Tea, and the recoveries of the pesticides spiked in these samples ranged from 75.1 to 118.4%. Chlorfenapyr and λ-cyhalothrin were found in the Tea samples bought randomly from local market. The results demonstrated that the developed SWCNTs-SPME method was a simple, efficient pretreatment and enrichment procedure for pesticides in complex matrices.     

基于自制聚苯胺顶空固相微萃取涂层快速监测水体和牛奶中的痕量多溴联苯醚

采用电化学沉淀法,成功地制备了多孔、高效聚苯胺固相微萃取涂层,并建立了顶空固相微萃取-气相色谱(HS-SPME-GC)快速测定水体和牛奶中的痕量多溴联苯醚的方法。详细研究了萃取模式、萃取温度、萃取时间、顶空体积及离子强度对萃取效率的影响。在优化实验条件下,本法测定的6种多溴联苯醚的线性范围为1~4000 ng/L(除BDE-154和BDE-153分别为1~3000 ng/L、1~2500 ng/L外),相关系数大于0.99,检出限(S/N=3)在0.08~0.20 ng/L之间,相对偏差小于8.5%(n=7)。自制聚苯胺涂层对多溴联苯醚的萃取效率优于商品化100μm-PDMS纤维。将本法用于河水和牛奶中痕量多溴联苯醚的测定,实际样品回收率分别在90%和80%以上。     

Comprehensive two-dimensional gas chromatography of polybrominated diphenyl ethers

Comprehensive two-dimensional gas chromatography with micro electron-capture detection (GCxGC-muECD) was evaluated for the separation of 125 polybrominated diphenyl ethers (PBDEs). From among the six column combinations that were evaluated, DB-1x007-65HT was found to be the most suitable because of: (i) the highest number of BDE congeners separated; (ii) the least decomposition of higher brominated congeners; and (iii) the most suitable maximum operating temperature. The separation of the 125 BDE congeners from five hydroxy- and two methoxy-BDEs and nine other brominated flame retardants (polybrominated biphenyls, tetrabromobisphenol-A, methyl-tetrabromobisphenol-A and hexabromocyclododecane) was also studied. Fluorinated BDEs were found to be valuable internal standards for the determination of BDEs because of their very similar physico-chemical properties and excellent separation from the parent BDEs, mainly in the second dimension. GCxGC-time-of-flight MS and GCxGC-muECD were shown to be useful tools to identify decomposition products of nona- and deca-substituted BDEs, which are formed during the GC run. Three nona-BDEs were shown to be the major decomposition products of BDE 209.     

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

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

Plunger-in-needle solid-phase microextraction with graphene-based sol-gel coating as sorbent for determination of polybrominated diphenyl ethers

A solid-phase microextraction (SPME) device, assembled with a commercially available plunger-in-needle microsyringe, with the plunger coated with graphene via a sol-gel approach, was developed for the gas chromatographic-mass spectrometric determination of polybrominated diphenyl ethers (PBDEs) in environmental samples. This is the first application of graphene-based sol-gel coating as SPME sorbent. Parameters affecting the extraction efficiency were investigated in detail. The new coating exhibited enrichment factors for PBDEs between 1378 and 2859. The unique planar structure of graphene enhanced the π-π interaction with the aromatic PBDEs; additionally, the sol-gel coating technique created a porous three-dimensional network structure which offered larger surface area for extraction. The stainless steel plunger provided firm support for the coating and enhanced the durability of the assembly. The plunger-in-needle microsyringe represents a ready-made tool for SPME implementation. Under the optimized conditions, the method detection limits for five PBDEs were in the range of 0.2 and 5.3 ng/L (at a signal/noise ratio of 3) and the precision (% relative standard deviation, n=5) was 3.2-5.0% at a concentration level of 100 ng/L. The linearities were 5-1000 or 10-1000 ng/L for different PBDEs. Finally, the proposed method was successfully applied to the extraction and determination by gas chromatography-mass spectrometry of PBDEs in canal water samples.     

Ultrasound-assisted leaching-dispersive solid-phase extraction followed by liquid-liquid microextraction for the determination of polybrominated diphenyl ethers in sediment samples by gas chromatography-tandem mass spectrometry

Ultrasound-assisted leaching-dispersive solid-phase extraction followed by dispersive liquid-liquid microextraction (USAL-DSPE-DLLME) technique has been developed as a new analytical approach for extracting, cleaning up and preconcentrating polybrominated diphenyl ethers (PBDEs) from sediment samples prior gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis. In the first place, PBDEs were leached from sediment samples by using acetone. This extract was cleaned-up by DSPE using activated silica gel as sorbent material. After clean-up, PBDEs were preconcentrated by using DLLME technique. Thus, 1 mL acetone extract (disperser solvent) and 60 μL carbon tetrachloride (extraction solvent) were added to 5 mL ultrapure water and a DLLME technique was applied. Several variables that govern the proposed technique were studied and optimized. Under optimum conditions, the method detection limits (MDLs) of PBDEs calculated as three times the signal-to-noise ratio (S/N) were within the range 0.02-0.06 ng g⁻¹. The relative standard deviations (RSDs) for five replicates were <9.8%. The calibration graphs were linear within the concentration range of 0.07-1000 ng g⁻¹ for BDE-47, 0.09-1000 ng g⁻¹ for BDE-100, 0.10-1000 ng g⁻¹ for BDE-99 and 0.19-1000 ng g⁻¹ for BDE-153 and the coefficients of estimation were ≥0.9991. Validation of the methodology was carried out by standard addition method at two concentration levels (0.25 and 1 ng g⁻¹) and by comparing with a reference Soxhlet technique. Recovery values were ≥80%, which showed a satisfactory robustness of the analytical methodology for determination of low PBDEs concentration in sediment samples.     

Dispersive liquid-liquid microextraction and gas chromatography-mass spectrometry determination of polychlorinated biphenyls and polybrominated diphenyl ethers in milk

An effective multi‐residue pretreatment technique, solid‐phase extraction (SPE) combined with dispersive liquid–liquid microextraction (DLLME), was proposed for the trace analysis of 14 polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in milk samples using gas chromatography–mass spectrometry (GC‐MS). Interesting analytes in milk samples were extracted with hexane after protein precipitation. The hexane extracts were loaded on an LC‐Florisil column to isolate analytes from the milk matrix. The elutes were dried and dissolved in acetone, which was used as the disperser solvent in subsequent DLLME procedures. The effects of several important parameters on the extraction efficiency were evaluated. Under the optimized conditions, a linear relationship was obtained in the range of 0.02–10.00 μg/L (PCBs) and 0.5–100.00 μg/L (PBDEs). The LOD (S/N=3) and relative standard deviations (RSDs, n=5) for all analytes were 0.01–0.4 μg/L and 0.6–8.5%, respectively. The recoveries of the standards added to raw bovine milk samples were 74.0–131.8%, and the repeatabilities of the analysis results were 1.12–17.41%. This method has been successfully applied to estimating PCBs and PBDEs in milk samples.     

Determination of phthalate esters in water samples by solid-phase microextraction and gas chromatography with mass spectrometric detection

Solid-phase microextraction (SPME) with an 85 microm polyacrylate fiber, coupled to gas chromatography-mass spectrometry was used to determine six phthalate esters and bis(2-ethylhexyl) adipate in water samples. The variables affecting the SPME absorption process were optimized and the method developed was applied to analyze both tap and commercial mineral water samples as well as water from the Ebro river and fishing and industrial ports. For real samples, the linear range in full scan acquisition mode was between 0.02 and 10 microg l(-1) for most compounds, and the limits of detection of the method were between 0.006 and 0.17 microg l(-1). Commercial water samples contained in recipients which were made from different materials were analyzed, and the influence of the material of the recipients on the concentration of phthalates was evaluated.     

Pesticide trace analysis using solid-phase extraction and gas chromatography with electron-capture and tandem mass spectrometric detection in water samples

Gas chromatography (GC) with electron-capture detection (ECD), mass spectrometry (MS) and tandem mass spectrometry (MS-MS) were employed for the identification of 12 pesticides in water samples. For this purpose, a solid-phase extraction procedure with C18 cartridges was used, optimising the breakthrough volume and the saturation concentration. In GC-MS-MS, the lowest detectable concentrations for the pesticides were between 2 and 26 ng l(-1), recoveries ranged from 70 to 133% in water samples spiked at 100 ng l(-1) and the relative standard deviations were in the range 5.3 to 17.4%. The proposed analytical methodology was applied to analyse pesticides in wetland samples from Almería (Spain).     

Simultaneous determination of "earthy-musty" odorous haloanisoles and their corresponding halophenols in water samples using solid-phase microextraction coupled to gas chromatography with electron-capture detection

Certain haloanisoles present at trace levels cause a large part of earthy-musty off-flavor problems in drinking water. These potent odorous chemicals come mainly through biomethylation of their corresponding halopenols. To enable the investigation of both families of compounds, a method involving solid-phase microextraction (SPME) was developed and the main parameters governing SPME were optimized. This method allows the simultaneous quantification of haloanisoles and halophenols at levels ranging from 1 to 100 or 250 ng/l, with detection limits of about 0.5 ng/l and could be applied to potable as well as raw surface waters.     

Extraction and determination of polybrominated diphenyl ethers in water and urine samples using solidified floating organic drop microextraction along with high performance liquid chromatography

We have developed a method, termed solidification of floating organic drop microextraction (SFOME), for the extraction of polybrominated diphenyl ethers (PBDEs) in water and urine samples, this followed by quantification via HPLC. This method requires very small quantities of organic solvent consumption. It is based on exposing a floating solidified drop of an organic solvent on the surface of aqueous solution in a sealed vial. The organic drop is easily collected with a spatula, molten (at ambient temperature), and then submitted to HPLC. Experimental parameters including extraction solvent and its volume, disperser solvent and its volume, extraction time, ionic strength, stirring speed and extraction temperature were optimized. The enrichment factors of analytes are in the range from 921 to 1,462, and acceptable extraction recoveries (92%–118%) are obtained. The dynamic linear range for five PBDE congeners is in the range of 0.5–75?μg.L^?1 and from 5 to 500?μg.L^?1 for BDE 209. The correlation coefficients range from 0.9960 to 0.9999. The limits of detection (at S/N?=?3) for PBDE congeners vary between 0.01 and 0.04?μg.L^?1. This method has been successfully applied to detecting PBDEs in two environmental waters and in human urine.

Determination of phthalates in water samples using polyaniline-based solid-phase microextraction coupled with gas chromatography

A simple solid-phase microextraction (SPME) device, coupled with gas chromatography-flame ionization detection (GC-FID), was developed to detect trace levels of phthalates in environmental water samples. Polyaniline (PANI) was chosen as the sorbent for the SPME device and was electrochemically deposited on a stainless steel wire to achieve high thermal and mechanical stability. The porous structure of the PANI film, characterized by scanning electron microscopy (SEM), suggested large extraction capability. Key parameters were optimized and five phthalates were selected to evaluate the SPME-GC procedures. The method was also applied to the analysis of lake and river water samples. Control experiments were carried out using commercial polyacrylate (PA) fiber. The new PANI-SPME-GC method offers high accuracy, precision and sensitivity and low detection limits. Thus, the method developed could be used as a new way to monitor the trace levels of phthalates in water medium. A possible extraction mechanism was investigated using electrochemical impedance spectroscopy (EIS).     

An organically modified silicate molecularly imprinted solid-phase microextraction device for the determination of polybrominated diphenyl ethers

An organically modified silicate (ORMOSIL) SPME stationary phase molecularly imprinted with BDE-209 has been successfully fabricated by conventional sol-gel technique from phenyltrimethoxysilane and tetraethoxysilane. The thickness of the ORMOSIL-SPME stationary phase, on fused-silica optical fibres, was measured to be ca. 9.5 μm with a volume of ca. 0.12 μL. Rebinding assays and Scatchard analysis revealed that the imprinted ORMOSIL-SPME stationary phase possessed a binding affinity, K_B, of 7.3 ± 1.7 × 10¹⁰ M⁻¹ for BDE-209, with a receptor site density, B_max, of 1.2 × 10⁻³ pmol per SPME device. Besides its molecular template, the ORMOSIL-SPME stationary phase also showed good affinity (log K_B ≥ 9.5) for smaller BDE congeners commonly found in the natural environment. The density of receptor sites within the imprinted matrix for those smaller BDE congeners was even higher than that for BDE-209. This may be attributable to the binding site heterogeneity of the imprinting process that creates deformed binding sites that are suitable for the accommodation of the smaller BDE congeners. Compared to the commercially available polyacrylate and polydimethylsiloxane SPME stationary phases, the imprinted ORMOSIL-SPME devices showed much higher pre-concentration ability towards polybrominated diphenyl ethers (PBDEs), even in direct immersion sampling at room temperature. Coupled with GC-NCI-MS and GC-μECD, the imprinted ORMOSIL-SPME device was able to achieve detection sensitivity of 0.2-3.6 pg mL⁻¹ and 1-8.8 pg mL⁻¹, respectively, for commonly occurring BDE congeners, including medium to high molecular weight PBDEs. The imprinted ORMOSIL-SPME device has been successfully applied to monitor PBDE contents in municipal wastewaters.     

Enrichment and determination of polybrominated diphenyl ethers in environmental water samples by magnetic solid‐phase extraction with core–shell magnetic carbon microspheres before gas chromatography with mass spectrometry

Core–shell magnetic carbon microspheres were synthesized by a simple hydrothermal method and used as a novel magnetic solid‐phase extraction adsorbent for the sensitive determination of polybrominated diphenyl ethers in environmental water samples. Gas chromatography with negative chemical ionization mass spectrometry was adopted for the detection. Box–Behnken design was used to investigate and optimize important magnetic solid‐phase extraction parameters through response surface methodology. Under the optimal conditions, low limits of detection (0.07–0.17 ng·L^?1), a wide linear range (1–1000 ng·L^?1), and good repeatability (0.80–4.58%) were achieved. The developed method was validated with several real water samples, and satisfactory results were obtained in the range of 72.8–97.9%. These results indicated that core–shell magnetic carbon microspheres have great potential as an adsorbent for the magnetic solid‐phase extraction of polybrominated diphenyl ethers at trace levels from environmental water samples.     

Analysis of polybrominated diphenyl ethers in atmospheric deposition and snow samples by solid-phase disk extraction

An extraction method for the quantitative analysis of polybrominated diphenyl ethers (PBDEs) in aqueous samples has been evaluated. The analytical methodology includes the sample filtration through glass fiber filter and subsequent extraction of dissolved phase compounds by C18 solid-phase disk extraction. Dependence of extraction efficiency on factors such as pollutant concentrations, sample volume, and stability during storage has been investigated. Mean extraction efficiencies of 97% for total PBDEs (13 tri- to heptabrominated congeners at spiking levels in the range of 15-90pg) with a RSD between 9 and 20% were achieved. Higher recoveries were observed for the more volatile PBDEs (112%) in relation to more brominated congeners (88%). The developed methodology was successfully applied to the analysis of these compounds in atmospheric deposition and snow samples from remote sites in Europe with method detection and quantitation limits in the range of 2.1-10pgL(-1) for almost all congeners, which allow the determination of PBDEs in remote areas with levels in the range of low to medium pgL(-1) for SigmaPBDEs.     

Large-volume programmed-temperature vaporiser injection for fast gas chromatography with electron capture and mass spectrometric detection of polybrominated diphenyl ethers

A large volume injection fast-GC-MS method has been developed, optimized and evaluated for the determination of polybrominated diphenyl ethers, including the decabrominated diphenyl ether (BDE-209). The programmed-temperature vaporiser injection parameters, temperature programming of the GC oven, and the physical dimensions of the narrow bore GC column were investigated to find the optimal operating conditions for the analysis. Depending on parameter settings the yield of the PBDEs and particularly BDE-209, varies significantly. Volumes up to 125 microl were successfully injected and a fast GC separation was performed, with retention times as short as 6.4 min for the last eluting compound, BDE-209. In a pilot study an air sample, collected at an electronics dismantling facility, was analyzed. Low-resolution mass spectrometry in electron capture negative ion mode was used for detection. Nine BDE congeners, including BDE-209, were identified and quantified.     

Determination of fungicides in natural waters using solid-phase microextraction and gas chromatography coupled with electron-capture and mass spectrometric detection

This study develops a method for the analysis of seven fungicides in environmental waters, using solid-phase microextraction (SPME). The analyzed compounds--dicloran, chlorothalonil, vinclozolin, dichlofluanid, captan, folpet and captafol--belong to different classes of chemical compound (chloroanilines, sulphamides, phthalimides and oxazolidines) and are used mainly in agriculture and as antifouling paints. Their determination was carried out by gas chromatography with electron-capture and mass spectrometric detection. To perform SPME, four types of fibre have been assayed and compared: polyacrylate (85 microm), polydimethylsiloxane (100 and 30 microm), carbowax-divinylbenzene (CW-DVB 65 microm) and polydimethylsiloxane-divinylbenzene (65 microm). The main parameters affecting the SPME process such as pH, salt additives, methanol content, memory effect, stirring rate and adsorption-time profile were studied. The method was developed using spiked natural waters such as ground water, sea water, river water and lake water in a concentration range of 0.1-10 microg/l. Limits of detection of studied compounds were determined in the range of 1-60 ng/l, by using electron-capture and mass spectrometric detectors. The recoveries of all fungicides were in relatively high levels (70.0-124.4%) and the average R2 values of the calibration curves were above 0.990 for all the analytes. The SPME conditions were finally optimized in order to obtain the maximum sensitivity. The potential of the proposed method was realized by applying it to the trace-level screening determination of fungicides and antifouling compounds in sea water samples originating from various Greek marinas.     

固相萃取-气相色谱-负化学源质谱法测定人血清中的多溴联苯醚

采用OasisHLB固相萃取柱萃取血清中的多溴联苯醚(PBDEs),经浓硫酸柱上除脂后,利用气相色谱-负化学源质谱法测定BDE-17、28、47、66、99、100、153、154、183和209共10种PBDEs组分。BDE-209的测定采用DB-5 ms色谱柱(15 m×0.25 mm×0.1 μm),其他组分采用VF-5 ms色谱柱(30 m×0.25 mm×0.25 μm)。对样品中蛋白质的去除溶剂和固相萃取条件(如洗脱溶剂及其用量)进行了优化。胎牛血清中的加标回收试验结果显示,各PBDEs单体相对于内标的平均回收率为78.5%～109.7%,日内测定的相对标准偏差(RSD)为0.3%～7.4%,日间测定的RSD为1.4%～14.1%。胎牛血清中三溴～七溴联苯醚的检出限(信噪比为3)为0.10～0.27 ng/L;定量限(信噪比为10)除了BDE-209为7.91 ng/L外,其他PBDEs为0.35～0.91 ng/L。采用本方法测定标准参考物质SRM1957和SRM1958,结果在参考值范围内。实验结果表明,本方法灵敏度高、准确度和精密度好,简便快速,溶剂消耗量少,适用于人体血清中三至十位溴取代联苯醚的测定。     

Investigation of photodegradation products generated after UV-irradiation of five polybrominated diphenyl ethers using photo solid-phase microextraction

In this study, the photoinduced degradation of five polybrominated diphenyl ethers (PBDEs), BDE-47, BDE-100, BDE-99, BDE-154 and BDE-153, is studied using solid-phase microextraction polydimethylsiloxane fibers as photolytic support. PBDEs are extracted from aqueous solutions using SPME fibers that are subsequently exposed to UV irradiation for different times (from 2 to 60 min). Photodegradation kinetics of the five PBDEs, tentative identification and photochemical behavior of the generated photoproducts, as well as photodegradation pathways, have been studied employing this on-fiber approach technique (photo-SPME) followed by gas chromatography-mass spectrometry analysis. Aqueous photodegradation studies have also been performed and compared with photo-SPME. All the photoproducts detected in the aqueous experiments were previously found in the photo-SPME experiments. In this study, reductive debromination by successive losses of bromine atoms is confirmed as the main photodegradation pathway of PBDEs. A large number of PBDEs were obtained as photoproducts of the five target analytes. Other mechanism of photodegradation observed was intramolecular cyclization from the homolytic dissociation of the C-Br bond; thus, polybromo-dibenzofurans were generated. This work contributes to the study of the photodegradation of PBDEs and shows the potential of photo-SPME to evaluate the photo-transformation of organic pollutants.     

Dispersive liquid-liquid microextraction followed by reversed phase-high performance liquid chromatography for the determination of polybrominated diphenyl ethers at trace levels in landfill leachate and environmental water samples

A simple, rapid and efficient method, dispersive liquid-liquid microextraction (DLLME), has been developed for the extraction and preconcentration of polybrominated diphenyl ethers (PBDEs) in water samples. The factors influencing microextraction efficiencies, such as the kind and volume of extraction and dispersive solvent, the extraction time and the salt effect, were optimized. Under the optimum conditions (sample volume: 5 mL; extraction solvent: tetrachloroethane, 20.0 μL; dispersive solvent: acetonitrile, 1.00 mL; extraction time: below 5 s and without salt addition), the enrichment factors and extraction recoveries were high and ranged from 268 to 305 and 87.0 to 119.1%, respectively. Linearity was observed in the range 0.05-50 ng mL⁻¹ for BDE-28 and BDE-99, and 0.1-100 ng mL⁻¹ for BDE-47 and BDE-209, respectively. Coefficients of correlation (r²) ranged from 0.9995 to 0.9999. The repeatability study was carried out by extracting the spiked water samples at concentration levels of 50 ng mL⁻¹ for BDE-28 and BDE-99, and 100 ng mL⁻¹ for BDE-47 and BDE-209, respectively. The relative standard deviations (R.S.D.s) varied between 3.8 and 6.3% (n = 5). The limits of detection (LODs), based on signal-to-noise ratio (S/N) of 3, ranged from 12.4 to 55.6 pg mL⁻¹ (the wavelength of detector at 226 nm). The relative recoveries of PBDEs from tap, lake water and landfill leachate samples at spiking levels of 5, 10 and 50 ng mL⁻¹ were in the range of 89.7-107.6%, 114.3-119.1% and 87.0-90.9%, respectively. As a result, this method can be successfully applied for the determination of PBDEs in landfill leachate and environmental water samples.