Multiresidue method for the simultaneous determination of four groups of pesticides in ground and drinking waters,using solid-phase microextraction-gas chromatography with electron-capture and thermionic specific detection

A common sample preparation procedure capable of efficiently concentrating various groups of pesticides, taking advantage of universal detectors like the mass spectrometer or combined techniques of group selective detectors like gas chromatography-electron capture detection (ECD)/thermionic specific detection (TSD), is desirable in environmental analysis. Six solid-phase microextraction fibres available for analysis of semi-volatiles (7, 30 and 100 microm poly(dimethylsiloxane) (PDMS), 85 microm polyacrylate, 60 microm PDMS-divinylbenzene (PDMS-DVB) and 65 microm Carbowax-DVB) were evaluated and the 60 microm PDMS-DVB was selected for the simultaneous extraction of 34 compounds, included in the organochlorine (OCPs), organophosphorous (OPPs), pyrethroid and triazine pesticide groups. All parameters affecting the extraction efficiency from water samples, namely fibre coating, sample agitation, pH and ionic strength, extraction temperature and time, were optimised. The analytical procedure involves solid-phase microextraction extraction, gas chromatographic separation and subsequent ECD and TSD via a post-column splitter adjusted to a split ratio of 1:10, respectively. Detection limits in the range of 1-10 ng l(-1) for OCPs, 1-30 ng l(-1) for OPPs, 20-30 ng l(-1) for pyrethroids and 8-50 ng l(-1) for triazines are easily attainable with the optimised procedure. The method validated for ground and drinking waters has low cost of implementation and operation although it requires careful maintenance.     

Development of a rapid and sensitive method for the simultaneous determination of 1,2-dibromoethane, 1,4-dichlorobenzene and naphthalene residues in honey using HS-SPME coupled with GC-MS

A new method for the simultaneous determination of 1,4-dichlorobenzene (p-DCB), naphthalene and 1,2-dibromoethane (1,2-DBE) residues in honey has been developed. Analysis is carried out using gas chromatography-mass spectrometry (GC/MS) in selected ion monitoring mode (SIM), after extraction and preconcentration of target analytes by headspace solid-phase microextraction (HS-SPME), with a 100 microm film thickness polydimethylsiloxane (PDMS) fiber. Several parameters affecting the extension of the adsorption process (i.e., addition of salt, extraction time, extraction temperature) were studied. The optimal conditions for the determination of these analytes were established. The proposed HS-SPME method showed good sensitivity, without carryover between the samples. Linearity was studied from 5 to 2500 microg kg(-1) for p-DCB, 0.5 to 500 microg kg(-1) for naphthalene and 5 to 500 microg kg(-1) honey for 1,2-DBE with correlation coefficients (r(2)) ranging from 0.9901 to 0.9999. Precision was assessed and both intra and inter-day R.S.D.s (%) were below 6.3%. The detection limits were found to be 1, 0.1 and 2 microg kg(-1) honey for p-DCB, naphthalene and 1,2-DBE, respectively. The percentage recoveries that were evaluated with the proposed HS-SPME method and the standard addition calibration technique gave values among 72.8 and 104.3% for measurements in samples spiked with one target analyte or mixtures of the three. This method has been applied for the analysis of unknown honey samples. The results showed an excellent applicability of the proposed method for the determination of the target compounds in honey samples.     

顶空固相微萃取-气相色谱-质谱法快速测定酱油中的挥发性风味成分

建立了一种快速简便地测定酱油中挥发性风味成分的顶空固相微萃取（HS-SPME）-气相色谱-质谱法(GC-MS)。以2-辛醇为内标,考察了萃取头、萃取时间、离子强度、萃取温度对酱油样品中挥发性风味物质萃取的影响。该方法对酱油中常见挥发性风味成分的测定有良好的重复性和回收率,对常见挥发性物质的定量比较准确。优化的HS-SPME条件为：涂层厚度为85 μm聚丙烯酸酯(PA)萃取纤维头,于45 ℃、NaCl质量浓度为250 g/L下对酱油样品顶空吸附40 min,于250 ℃下解吸2 min后进行GC-MS分离鉴定。酱油样品的分析结果表明,其挥发性风味物质中含量较高的是醇、酸、酯和酚类,此外还有一些羰基化合物和杂环化合物。     

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.     

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.     

Evaluation of headspace solid-phase microextraction for analysis of phosphine residues in wheat

In headspace (HS) analysis, a fumigant is released from a commodity into a gas-tight container by grinding, heating, or microwaves. A new technique uses HS-solid-phase microextraction (SPME) for additional preconcentration of fumigant. HS-SPME was tested for detection of phosphine (PH3), chosen for examination because of its wide use on stored commodities. PH3 was applied to 50 g wheat in separate 250 mL sealed flasks, which were equipped either with a septum for conventional HS analysis or with one of four HS-SPME fibers [100 microm polydimethylsiloxane (PDMS), 85 microm carboxen (CAR)/PDMS, 75 microm CAR/PDMS, and 65 pm PDMS/divinylbenzene (DVB)]. The wheat was heated at 45 degrees C for 20 min. In conventional HS analysis, a gaseous aliquot (80 pL) was taken from the HS and injected into the GC instrument. In the HS-SPME procedure, the fiber was removed from the HS and exposed in the heated injection port of the GC instrument. In all cases, PH3 was determined under the same chromatographic conditions with a GC pulsed flame photometric detector. In a comparison of the efficacy of the fibers, the bipolar fibers (CAR/PDMS and PDMS/DVB) contained more PH3 than the aliquot in the conventional HS analysis; larger size bipolar fibers extracted PH3 more efficiently than smaller fibers (e.g., 85 > 75 > 65 microm). The nonpolar fiber (PDMS) contained no PH3. Four fortification levels of PH3 on wheat were tested: 0.01, 0.05, 0.1, and 0.3 microg/g. The response of each bipolar fiber increased with the fortification levels, but the conventional HS analysis detected no fumigant at the lowest fortification level of 0.01 mg/g. Under the conditions of the validation study, the LOD was in the range of 0.005-0.01 ng PH3/g wheat.     

Studies on the aroma of cupuassu liquor by headspace solid-phase microextraction and gas chromatography

Headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography with ion trap mass spectrometric detection and with atomic emission detection (GC-AED) was employed to identify possible odor-impact volatile organic compounds in cupuassu (Theobroma grandiflorum Spreng) liquor, as well as to quantify alkylpyrazines present in these samples. SPME fibers coated with 100 microm polydimethylsiloxane (PDMS), 65 microm PDMS-divinylbenzene (DVB) and 75 microm Carboxen (CAR)-PDMS were tested, the later being chosen for the optimized extraction procedure. The principal compounds found in the sample headspace were 3-methylbutanal, dimethylsulfide, dimethyldisulfide, beta-linalool and several alkylpyrazines (notably tetramethylpyrazine). The procedure for quantitation of the alkylpyrazines, using GC-AED for their separation and detection, allowed the detection of microg g(-1) levels of the analytes in the samples, with acceptable precision (R.S.D. less than 10%).     

Determination of pyrethroid residues in tobacco by means of solid phase microextraction and GC/MS with the aid of ultrasonic assisted extraction using water as extracting solvent.

A rapid and simple sampling approach using solid phase microextraction (SPME) for pyrethroid residues analysis in flue-cured tobacco was studied. The fibers coated with poly-dimethylsiloxane (PDMS) at 100 microm thickness were chosen. Extraction time of 180 s, desorption time of 120 s and desorption temperature of 280 degrees C were selected. The whole sampling process, only including an ultrasonic assisted extraction step and a solid phase microextraction step, can be completed within 15 min. The associated SPME and ultrasonic assisted extraction using water as extracting solvent shows good results for tobacco pyrethroid residues determination. Results indicated that four pyrethroids can be determined simultaneously, and the limits of detection are below 35 ng g(-1) using GC/MS in selected ion monitoring (SIM) mode. The reproducibility of the technique is found to be better than 11.8% RSD.     

Headspace solid phase microextraction in-situ supercritical fluid extraction coupled to gas chromatography-tandem mass spectrometry for simultaneous determination of perfluorocarboxylic acids in sediments

Headspace solid phase microextraction (HS-SPME) in-situ supercritical fluid extraction (SFE) was investigated for the determination of trace amounts of perfluorocarboxylic acids (PFCAs) in sediments. Quantitation was performed by using gas chromatography coupled to negative chemical ionization-tandem mass spectrometry (GC-NCI-MS/MS). The optimum conditions of HS-SPME following SFE were obtained using 500 μL n-butanol as a derivatization reagent in supercritical carbon dioxide with static extraction for 10 min, then dynamic extraction for 20 min at 30 MPa and 70 °C and simultaneous collected with 100 μm film thickness PDMS fiber. The linear range of proposed method was from 5 to 5000 ng g(-1), with limit of detection ranging from 0.39 to 0.54 ng g(-1) and limit of quantitation ranging from 1.30 to 1.80 ng g(-1). The developed method was successfully applied to analyze PFCAs in sediments from rivers and beach near industrial areas. The concentrations of PFCAs determined are from 282 to 4473 ng g(-1).     

Poly(phthalazine ether sulfone ketone) as novel stationary phase for stir bar sorptive extraction of organochlorine compounds and organophosphorus pesticides

A novel poly(phthalazine ether sulfone ketone) (PPESK) film prepared by immersion precipitation technique was coated on stir bars for sorptive extraction. Scanning electron micrographs showed that the coating has a denser porous surface (about 1 microm in thickness) with a sponge-like sublayer, and the thickness of the coating was 250 microm. The PPESK coated stir bar has high thermostability (290 degrees C) and long lifetime (50 times). The extraction properties of this stir bar were evaluated for the extraction of both polar and semi-polar analytes, including organochlorine compounds and organophosphorus pesticides. The PPESK stir bar was proved to show higher affinity towards polar compounds than that of PDMS coated stir bar and higher sample load compared with corresponding PPESK fiber. It was applied to the determination of organochlorine compounds in seawater samples and organophosphorus pesticides in juices by gas chromatographic analysis. The effect of sample matrix was evaluated at optimized condition of extraction temperature, extraction time and salt concentration. Limits of detection were in the range of 0.05-2.53 ng L(-1) for organochlorine compounds in seawater samples using electron capture detector (ECD), with precisions of less than 11% RSD. Limits of detection for organophosphorus pesticides were in the range of 0.17-2.25 ng L(-1) and 2.47-10.3 ng L(-1) in grape and peach juice, respectively, using thermionic specified detector (TSD), with precisions of less than 12% RSD and 20% RSD, respectively.     

Stir bar sorptive extraction and comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry for ultra-trace analysis of organochlorine pesticides in river water

A method for the determination of ultra-trace amounts of organochlorine pesticides (OCPs) in river water was developed by using stir bar sorptive extraction (SBSE) followed by thermal desorption and comprehensive two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry (SBSE-TD-GC×GC-HRTOF-MS). SBSE conditions such as extraction time profiles, phase ratio (β: sample volume/polydimethylsiloxane (PDMS) volume), and modifier addition, were examined. Fifty milli-liter sample including 10% acetone was extracted for 3 h using stir bars with a length of 20 mm and coated with a 0.5 mm layer of PDMS (PDMS volume, 47 μL). The stir bar was thermally desorbed and subsequently analyzed by GC×GC-HRTOF-MS. The method showed good linearity over the concentration range from 50 to 1000 pg L(-1) or 2000 pg L(-1) for all analytes, and the correlation coefficients (r(2)) were greater than 0.9903 (except for β-HCH, r(2)=0.9870). The limit of detection (LOD) ranged from 10 to 44 pg L(-1). The method was successfully applied to the determination of 16 OCPs at pg L(-1) to ng L(-1) in river water. The results agree fairly well with the values obtained by a conventional liquid-liquid extraction (LLE)-GC-HRMS (selected ion monitoring: SIM) method using large sample volume (20 L). The method also allows screening of non-target compounds, e.g. pesticides and their degradation products, polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and pharmaceuticals and personal care products (PPCPs) and metabolites in the same river water sample, by using full spectrum acquisition with accurate mass in GC×GC.     

Determination of diisopropylfluorophosphate in rat plasma and brain tissue by headspace solid-phase microextraction gas chromatography/mass spectrometry

A simple, sensitive and rapid method for the determination of diisopropylfluorophosphate (DFP) in rat plasma and brain tissue using headspace solid-phase microextraction (HS-SPME) and gas chromatography/mass spectrometry (GC/MS) is presented. A 65 microm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was selected for sampling. The main parameters affecting the SPME process such as extraction and desorption temperature, extraction and desorption time, salt addition, and fiber preheating time were optimized in each matrix to enhance the extraction efficiency of the method. The lower limits of quantitation for DFP in plasma and brain tissue were 1 ng/mL and 3 ng/g, respectively. The method showed good linearity over the range from 1-100 ng/mL in plasma and 3-300 ng/g in brain tissue with correlation coefficient (R(2)) values higher than 0.995. The precision and accuracy for intra-day and inter-day were less than 10%. The relative recoveries in plasma and brain for DFP were greater than 50%. Stability tests including autosampler and freeze and thaw were also investigated. This validated method was successfully applied to study the neurobehavioral effects of low-level organophosphate exposures. Copyright (c) 2008 John Wiley & Sons, Ltd.     

Development of solid-phase extraction and solid-phase microextraction methods for the determination of chlorophenols in cork macerate and wine samples

Tri-, tetra- and pentachlorophenol (TCP, TeCP and PCP) can be considered the precursors in the formation of corresponding chloroanisoles, known to be powerful odorants in corks and wine. Determining the presence of these chlorophenolic compounds in cork soaking solutions (ethanol/water mixtures, 12% (v/v) ethanol used for cork quality control testing), or in wine can be achieved by acetylation/gas chromatography electron-capture detection. In order to reach the required sensitivity, a previous preconcentration step is necessary. Solid-phase extraction (SPE) and headspace solid-phase microextraction (HS-SPME) have given good results for the preconcentration of TCP, TeCP and PCP in such matrices. The use of Oasis HLB cartridges gives acceptable recoveries for the three compounds when different volumes (50-250 mL) of cork macerate with concentrations ranging from 20 to 150 ng/L are processed. Preconcentration based on HS-SPME has also been optimised with a 100 microm polydimethylsiloxane fibre and in situ derivatization. The HS-SPME method allows chlorophenols in a cork soaking solution and in wine to be determined with a limit of detection of 1 ng/L for each compound (in cork macerate) and a repeatability of around 0.5%-5% (n=8) for a concentration level of 30 ng/L.     

Application of a novel sol-gel polydimethylsiloxane-poly(vinyl alcohol) solid-phase microextraction fiber for gas chromatographic determination of pesticide residues in herbal infusions

A simple and environmentally friendly methodology for headspace solid-phase microextraction (HS-SPME) using a new fiber coated with polydimethylsiloxane-poly(vinyl alcohol) (PDMS/PVA) is reported for the trace determination of organochlorine (OCP) and organophosphorus (OPP) pesticides in herbal infusions of Passiflora L. by GC-ECD. The capacity of the PDMS/PVA coating for the pesticides was compared to that of commercial PDMS fibers, with advantageous results. The effects of parameters such as the sample ionic strength, dilution of the infusion, extraction temperature and time were investigated. The optimized conditions for the determination of OCP and OPP in Passiflora L. infusions were extraction time and temperature, respectively, of 38 min and 67.5 degrees C, with 5 min of sample/headspace equilibration time. The analytical curves for the range between 0.04 ng mL(-1) to 6 ng mL(-1) of each compound presented a good quality (correlation coefficients of 0.921 or better). The detection limits for the OCP and OPP in these matrices varied from 0.01 ng mL(-1) (beta-endosulfan) to 1.5 ng mL(-1) (malathion). The sensitivity of studied methodology was adequate, as well as its accuracy (78.7-91.5%) and precision (R.S.D. = 1.2-14.2%).     

Qualitative evaluation of thermal desorption-programmable temperature vaporization-comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry for the analysis of selected halogenated contaminants

The separation of 38 toxic and predominant polychlorinated biphenyl (PCB) congeners, 11 persistent halogenated pesticides, 1 brominated biphenyl (BB), and 8 polybrominated diphenyl ethers (PBDEs) has been optimized using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC x GC-TOFMS). A thermal desorption-programmable temperature vaporization (TD-PTV) step was used for the injection. Different column sets were investigated, and a 100% dimethylpolysiloxane (15 m x 0.25 mm i.d. x 0.25 microm film thickness) narrowbore capillary column coupled to a high temperature (8% phenyl)-polycarborane-siloxane (2 m x 0.10 mm i.d. x 0.10 microm film thickness) microbore column set was selected. Of the 58 compounds investigated, only one pair of PCBs was not resolved. All other analytes were either baseline separated into the chromatographic plane or were virtually separated using the deconvolution capability of the TOFMS.     

Multiresidue determination of organochlorine pesticides and polychlorinated biphenyls in milk by gas chromatography with electron-capture detection after extraction by matrix solid-phase dispersion

A multiresidue analytical method based on matrix solid-phase dispersion was developed to analyze liquid milk for 22 organochlorine pesticides (OCPs) and 6 polychlorinated biphenyls (PCBs). Initial extraction is performed by loading 3 mL milk onto a 2.0 g octadecyl (C18)-bonded silica cartridge with n-hexane as the eluant. Neutral alumina column chromatography with sodium sulfate as the drying agent is used for further cleanup. The eluate is concentrated to 0.5 mL, and target analytes are determined by capillary gas chromatography with electron-capture detection. The optimized method was validated by determining accuracy (recovery percentages), precision (repeatability and reproducibility), and sensitivity (detection and quantitation limits) from analyses of milk samples fortified at 10 and 1 microg/L levels. Average recoveries were between 74 and 106% for all residues except beta-HCH, beta-endosulfan, and endosulfan sulfate. Both repeatability and reproducibility relative standard deviation values were < 22% for all residues. Detection limits ranged from 0.02 to 0.12 microg/L and quantitation limits were between 0.02 and 0.62 microg/L. The proposed analytical method may be used as a fast and simple procedure in routine determinations of OCPs and PCBs in milk.     

A solid phase extraction method for the screening and determination of pyrethroid metabolites and organochlorine pesticides in human urine.

A screening method has been developed for the determination of 23 organochlorine pesticides (OCPs) and 3-pyrethroid metabolities [cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid, cis-3-(2,2-dibromovinyl)-2,2-dimethyl-(1-cyclopropane) carboxylic acid and 3-phenoxybenzoic acid] from human urine. OCPs were directly detected in urine samples while pyrethroid metabolites required acid-induced hydrolysis to convert their conjugates into free acids; all compounds were then cleaned-up/preconcentrated using solid phase extraction. Determination and quantitation was achieved by gas chromatography with a mass spectrometer detector operating in selected ion monitoring mode. Limits of detection varied between 0.1 and 0.3 ng/mL with linear ranges from 0.3 to 700 ng/mL; the precision of the method was high (4.3-7.2%). Recoveries of all analytes from urine samples fortified at levels of 30 ng/mL for each OCP and 15 ng/mL for each pyrethroid metabolite ranged from 88 to 101% (captan gave the lowest recovery). The results obtained from the analysis of real urine samples show the suitability of the proposed method for monitoring people exposed to organochlorine and pyrethroid pesticides.     

Dodecylsulfate-doped polypyrrole film prepared by electrochemical fiber coating technique for headspace solid-phase microextraction of polycyclic aromatic hydrocarbons

The electrochemical fiber coating (EFC) technique was used for the preparation of dodecylsulfate-doped polypyrrole (PPy-DS), and applied as a new fiber for solid-phase microextraction (SPME) procedures. PPy-DS film was directly electrodeposited on the surface of a platinum wire from an aqueous solution containing pyrrole and sodium dodecylsulfate, using cyclic voltammetry (CV). The effect of polymerization conditions and type of dopants on the thermal stability, adhesion and extraction characteristics of the fiber were investigated. The electron microscopy imaging of PPy-DS film suggested that the surface fiber coating was well-distributed with a porous structure. The fiber coating can be prepared easily in a reproducible manner, and it is inexpensive and has a stable performance at high temperatures (up to the 300 degrees C). The extraction properties of the fiber to eight polycyclic aromatic hydrocarbons (PAHs) were examined, using a headspace-SPME (HS-SPME) device coupled with gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The results revealed study shows that PPy-DS as a SPME fiber coating is suitable for the successful extraction of PAHs. The effects of the extraction parameters including exposure time, sampling temperature, salt concentration, and stirring rate on the extraction efficiency have been studied. A satisfactory reproducibility for extractions from spiked water samples at PPb-level with R.S.D. < 7.6% (n = 7) was obtained. The calibration graphs were linear in the range of 0.5-100ng ml(-1) and detection limits for the selected PAHs were between 0.05-0.16 ng ml(-1). Comparing the HS-SPME results for extraction and determination of PAHs using PPy-DS fiber with the corresponding literature data using PDMS fiber shows that the proposed fiber has a better detection limit for low molecular weight PAHs. The life span and stability of PPy-DS fiber is good and it can be used more than 50 times at 250 degrees C without any significant change in sorption properties.     

Sol-gel coated polydimethylsiloxane/beta-cyclodextrin as novel stationary phase for stir bar sorptive extraction and its application to analysis of estrogens and bisphenol A

A sol-gel technique was used for the preparation of a stir bar coated with a composite composed of polydimethysiloxane and beta-cyclodextrin (PDMS/beta-CD). The sol-gel mechanism during coating procedure was discussed and successful binding of beta-CD to the sol-gel network was confirmed by the IR spectra. Scanning electron micrographs of the stir bars revealed a homogeneous surface with a film thickness of 30-150 microm attributing to different coating times. Good thermal stability and solvent-resistance of the stir bar were found thanks to chemical binding formed between the stationary phase and the glass substrate. The PDMS/beta-CD coated stir bar was proved to have better selectivity to polar compounds compared to the PDMS coated stir bar, and higher extraction capacity compared to the corresponding PDMS/beta-CD coated fiber. Methods for the determinations of estrogens in environmental water, bisphenol A in drinking water and in leachate of one-off dishware by the PDMS/beta-CD coated stir bar coupled with high-performance liquid chromatography (HPLC) were developed. The limits of detection were within the range of 0.04-0.11 microg l(-1) for estrogens using UV detection and 8 ngl(-1) for bisphenol A using fluorescence detection. Reproducibility with RSD less than 9.7% for extractions of real water samples at microg l(-1) or ngl(-1) level was obtained.     

Determination of odorous mixed chloro-bromoanisoles in water by solid-phase micro-extraction and gas chromatography-mass detection

A headspace-solid-phase micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) method has been proposed for the simultaneous determination of odorous trihalogenated anisoles in water. Parameters affecting efficiency of HS-SPME procedure, such as the selection of the SPME coating, extraction time, temperature and ionic strength were optimized. The commercially available polydimethylsiloxane (PDMS 100 microm) fiber appears to be the most suitable for the simultaneous determination of these compounds. Run-to-run precision with relative standard deviations (R.S.D.s) between 5 and 15% were obtained for most of the compounds except for 2,5-dicloro-6-bromo-anisole, 2,3-dibromo-6-chloroanisole, pentachloro- and pentabromoanisole (>20%). The method was linear over two orders of magnitude, and detection limits were compound dependent and ranged from 0.03 ng/L for 2,4,6-trichloroanisole to 0.25 ng/L for 2,3-dibromo-6-chloroanisole. The HS-SPME-GC-MS procedure was tested using real samples and relatively good standard deviations were obtained when using p-iodoanisole as internal standard for quantification. This is the first time that the individual identification of odorous trihalogenated chloro-bromoanisoles has been reported, being HS-SPME-GC-MS a suitable method for simultaneous determination of these compounds in water at concentration levels below their odor limit of detection.