Stir bar sorptive extraction and trace analysis of alkylphenols in water samples by thermal desorption with in tube silylation and gas chromatography-mass spectrometry

A novel method called thermal desorption (TD) with in tube silylation followed by gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of alkylphenols (APs) in river water samples, is described. APs are extracted from river water samples and concentrated by the stir bar sorptive extraction (SBSE) technique. The stir bar coated with polydimethylsiloxane (PDMS) is added to 2.0 ml water sample and stirring is carried out for 60 min at room temperature (25 degrees C) in the vial. Then, the PDMS stir bar is subjected to TD with in tube silylation followed by GC-MS. The detection limit is of the sub pg ml(-1) (ppt) level. The method shows good linearity and the correlation coefficients are higher than 0.99 for all analytes. The average recoveries of APs are higher than 90% (R.S.D.: 3.6-14.8%, n=6). This simple and sensitive analytical method may be used in the determination of trace amounts of APs in river water samples.     

Microwave-assisted extraction followed by gas chromatography-mass spectrometry for the determination of endocrine disrupting chemicals in river sediments

A method for the simultaneous measurement of trace amounts of phenolic xenoestrogens, such as 2,4-dichlorophenol (2,4-DCP), 4-tert-butyl-phenol (BP), 4-tert-octylphenol (OP), 4-nonylphenol (NP), pentachlorophenol (PCP) and bisphenol A (BPA), in water samples was developed using stir bar sorptive extraction (SBSE) with in situ derivatization followed by thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS) analysis. The conditions for derivatization with acetic acid anhydride were investigated. A polydimethylsiloxane (PDMS)-coated stir bar and derivatization reagents were added to 10 ml of water sample and stirring was commenced for 10-180 min at room temperature (25 degrees C) in a headspace vial. Then, the extract was analyzed by TD-GC-MS. The optimum time for SBSE with in situ derivatization was 90 min. The detection limits of 2,4-DCP, BP, OP, NP, PCP and BPA were 2, 1, 0.5, 5, 2 and 2 pg ml(-1), respectively. The method showed good linearity over the concentration ranges of 10, 5, 2, 20, 10 and 10-1000 pg ml(-1) for 2,4-DCP, BP, OP, NP, PCP and BPA, respectively, and the correlation coefficients were higher than 0.99. The average recoveries of those compounds in river water samples were equal to or higher than 93.9% (R.S.D. <7.2%) with correction using the added surrogate standards. This simple, accurate, sensitive and selective method can be used in the determination of trace amounts of phenolic xenoestrogens in river water samples.     

Determination of 4-nonylphenol and 4-tert.-octylphenol in water samples by stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry

A simple and highly sensitive method called thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of 4-nonylphenol (NP) and 4-tert.-octylphenol (OP) in water samples, is described. NP and OP in samples are extracted from water samples and concentrated by the stir bar sorptive extraction (SBSE) technique. A stir bar coated with polydimethylsiloxane (PDMS) is added to a 2.0 ml water sample and stirring is carried out for 60 min at room temperature (25 °C) in a headspace vial. Then the extract is high sensitively analyzed by TD-GC-MS without any derivatization step. The optimum SBSE conditions are realized at an extraction time of 60 min. The detection limits are 0.02 ng ml⁻¹ for NP and 0.002 ng ml⁻¹ for OP. The method shows good linearity over the concentration range of 0.1-10 ng ml⁻¹ for NP and 0.01-10 ng ml⁻¹ for OP, and the correlation coefficients are higher than 0.999. The average recoveries of NP and OP are higher than 97% (R.S.D.: 3.6-6.2%) with correction using the added surrogate standards, 4-(1-methyl) octylphenol-d₅ and deuterium 4-tert.-octylphenol. This simple, accurate, sensitive and selective analytical method may be used in the determination of trace amounts of NP and OP in tap and river water samples.     

Stir bar sorptive extraction with in situ derivatization and thermal desorption-gas chromatography-mass spectrometry for determination of chlorophenols in water and body fluid samples

A new method, stir bar sorptive extraction (SBSE) with in situ derivatization and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS), which is used for the determination of trace amounts of chlorophenols, such as 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TrCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP) and pentachlorophenol (PCP), in tap water, river water and human urine samples, is described. The derivatization conditions with acetic acid anhydride and the SBSE conditions such as extraction time are investigated. Then, the stir bar is subjected to TD followed by GC-MS. The detection limits of the chlorophenols in tap water, river water and human urine samples are 1-2, 1-2, and 10-20 pg ml⁻¹ (ppt), respectively. The calibration curves for the chlorophenols are linear and have correlation coefficients higher than 0.99. The average recoveries of the chlorophenols in all the samples are higher than 95% (R.S.D. < 10%) with correction using added surrogate standards, 2,4-dichlorophenol-d₅, 2,4,6-trichlorophenol-¹³C₆, 2,3,4,6-tetrachlorophenol-¹³C₆ and pentachlorophenol-¹³C₆. This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of chlorophenols in liquid samples.     

Stir bar sorptive extraction with in situ derivatization and thermal desorption-gas chromatography-mass spectrometry for trace analysis of methylmercury and mercury(II) in water sample

A method for the trace analysis of methylmercury (MeHg) and Hg(II) in water sample was developed, which involved stir bar sorptive extraction (SBSE) with in situ alkylation with sodium tetraethylborate and thermal desorption (TD)-gas chromatography-mass spectrometry (GC-MS). The limits of quantification of MeHg and Hg(II) are 20 and 10 ng L⁻¹ (Hg), respectively. The method shows good linearity and the correlation coefficients are higher than 0.999. The average recoveries of MeHg and Hg(II) in tap or river water sample are 102.1-104.3% (R.S.D.: 7.0-8.9%) and 105.3-106.2% (R.S.D.: 7.4-8.5%), respectively. This simple, accurate, sensitive, and selective analytical method may be used in the determination of trace amounts of MeHg and Hg(II) in tap and river water samples.     

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.     

Dual derivatization-stir bar sorptive extraction--thermal desorption--gas chromatography-mass spectrometry for determination of 17beta-estradiol in water sample

A novel method for the trace analysis of 17beta-estradiol (E2) in river water sample was developed, which involved stir bar sorptive extraction (SBSE) with in situ acylation (first derivatization) and thermal desorption (TD) with quartz wool assisted (QWA) in tube silylation (second derivatization), followed by gas chromatography-mass spectrometry (GC-MS), and is called the "dual derivatization method." The optimum conditions for SBSE with in situ acylation, such as the volume of acetic acid anhydride and the extraction time, were investigated. In addition, the optimum conditions for TD with QWA in tube silylation, such as the volume of N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and the TD temperature and hold time, were investigated as well. The detection limit (S/N = 3) and the quantitation limit (S/N>10) of E2 in the river water sample were 0.5 and 2 pg ml(-1) (ppt), respectively, by the dual derivatization method. In addition, the detection limit was 0.1 pg ml(-1) by using dual derivatization method with multi-shot mode. The calibration curve for E2 was linear in the range of 0.002-10 ng ml(-1) with correlation coefficients >0.999. The average recoveries of E2 (n = 6) at the concentrations of 0.05 and 1.0 ng ml(-1) from the river water sample were 93.1 (RSD: 1.4%) and 98.4% (RSD: 0.8%), respectively, with correction using the added surrogate standard, 17beta-estradiol-(13)C(4). This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of E2 in water samples.     

Stir bar sorptive extraction coupled to thermodesorption-gas chromatography-mass spectrometry for the determination of insect repelling substances in water samples

Stir bar sorptive extraction (SBSE) in combination with thermodesorption-gas chromatography-mass spectrometry (TD-GC-MS) was applied for the determination of eight insect repellents and synergists in water samples. The stir bar coated with polydimethylsiloxane (PDMS) was added to 20 mL of water sample with 4 g NaCl and stirred at 1000 rpm for 180 min. Then, the stir bar was subjected to TD-GC-MS. SBSE parameters (ionic strength, presence of organic solvent and time) were optimised. Blank contamination and carryover problems were also studied. The method affords detection limits between 0.5 and 30 ng/L, except for dimethyl phthalate (DMP) (150 ng/L) due to blank contamination problems. It shows good linearity with correlation coefficients over 0.997 and reproducibility (RSD) below 20%. The extraction efficiencies were between 29% for DMP and 80% for di-n-propyl isocinchomeronate (R-326). The feasibility of the method was tested by analysing real samples such as lake water, river water and wastewater.     

固相微萃取-气相色谱法测定白洋淀水样中的邻苯二甲酸酯类化合物

建立了固相微萃取(SPME)-气相色谱法(GC)分析环境水样中痕量邻苯二甲酸酯类化合物(PAEs)的方法。选用100 μm聚二甲基硅烷(PDMS)萃取纤维,在磁力搅拌条件下,对水样中的PAEs萃取富集60 min,然后直接注入GC进样口,在250 ℃温度下解吸4 min后进行分析测定,13种PAEs能得到充分提取和分离。方法的重现性(以相对标准偏差(RSD)计为0.2%～9.7%,检出限为0.02～0.83 μg/L。将本方法应用于白洋淀水样中PAEs的分析检测发现,样品中邻苯二甲酸二异丁酯(DIBP)、邻苯二甲酸二丁酯(DBP)、邻苯二甲酸二(2-乙基己基)酯(DEHP)检出率相对较高。对水样进行两个浓度水平(2.5 μg/L和5.0 μg/L)的加标试验,加标回收率为75.3%～111.0%,RSD为2.1%～8.0%(n=3),能够满足环境水样中痕量PAEs的测定要求。     

Liquid phase microextraction with in situ derivatization for measurement of bisphenol A in river water sample by gas chromatography-mass spectrometry

A new method that involves liquid phase microextraction (LPME) with in situ derivatization and gas chromatography-mass spectrometry (GC-MS) is described for the determination of trace amounts of bisphenol A (BPA) in river water samples. The LPME conditions, such as the type of extraction solvent and the extraction time, are investigated. Then, the extract is directly injected into GC-MS. The detection limit and the quantification limit of BPA in river water sample are 2 and 10pgml(-1) (ppt), respectively. The calibration curve for BPA is linear with a correlation coefficient of >0.999 in the range of 10-10,000pgml(-1). The average recoveries of BPA in river water samples spiked with 100 and 1000pgml(-1) BPA are 104.1 (RSD: 8.9%) and 98.3 (RSD: 3.2%), respectively, with correction using the added surrogate standard, bisphenol A-(13)C(12). This simple, accurate, sensitive and selective analytical method may be applicable to the determination of trace amounts of BPA in liquid samples.     

PDMS Rod-SBSE System Coupled with Gas Chromatography for Determination of PAHs in Aqueous Samples

A method for the analysis of trace polycyclic aromatic hydrocarbons(PAHs) in aqueous samples has been established by polydimethylsiloxane(PDMS) rod aided stir bar sorptive extraction(SBSE). The homemade PDMS rod has a size of 30 mm?3 mm o.d. with a volume of ca. 200 ?L, stable in thermal desorption process. The enriched PAHs by the PDMS rod were released in a homemade thermal desorption system coupled with gas chromatography. Experimental parameters for extraction of six PAHs were optimized including extraction time, pH, ionic strength and temperature of solution. The procedure has good recoveries of 80.0%―100.3% and very low limits of detection of 4.0―33 ng/L. PAHs in rain and river water were analyzed by this method.     

Development of a method for the determination of UV filters in water samples using stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry

Stir bar sorptive extraction (SBSE) in combination with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) was applied for the determination of 9 UV filters in water samples. The stir bar coated with polydimethylsiloxane (PDMS) was added to 20 mL of water sample at pH 2 (10% MeOH) and stirred at 1000 rpm for 180 min. Then, the stir bar was subjected to TD-GC-MS. The desorption conditions (desorption temperature and desorption time) and SBSE parameters (ionic strength, pH, presence of organic solvent and time) were optimised using a full factorial design and a Box-Behnken design, respectively. The method shows good linearity (correlation coefficients >0.994) and reproducibility (RSD<16%). The extraction efficiencies were above 63% for all the compounds. Detection limits were between 0.2 and 63 ng/L. The developed method offers the ability to detect several UV filters at ultra-low concentration levels with only 20 mL of sample volume. The effectiveness of the method was tested by analysing real samples such as lake water, river water and treated wastewater. The application of the method allowed reporting the levels of UV filters in environmental water samples.     

Stir bar sorptive extraction for the analysis of short‐chain chlorinated paraffins in water

An optimised method using stir bar sorptive extraction (SBSE) and a thermal desorption‐GC‐electron capture detector (GC‐ECD) for the determination of short‐chain chlorinated paraffins from water samples was developed. Recoveries near to 100% were obtained by using 20 mm×0.5 mm (length×film thickness) PDMS commercial stir bars from 200 mL spiked water samples and 20% methanol addition with an extraction period of 24 h. Method sensitivity, linearity and precision were evaluated for surface water and wastewater spiked samples. A LOD of 0.03 and 0.04 μg/L was calculated for surface and wastewater, respectively. The precision of the method given as an RSD was below 20% for both matrices. The developed method was applied for the analysis of two real samples from a contaminated river and a wastewater treatment plant. Results were in accordance with those obtained using a previously developed method based on solid phase microextraction (SPME).     

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.     

Parts per trillion level determination of endocrine-disrupting chlorinated compounds in river water and wastewater effluent by stir-bar-sorptive extraction followed by gas chromatography–triple quadrupole mass spectrometry

A new analytical method using stir-bar-sorptive extraction (SBSE) followed by liquid desorption (LD) and gas chromatography with triple-quadrupole mass spectrometric detection (GC-QqQ-MS-MS) has been used for quantitative determination of 25 chlorinated endocrine-disrupting compounds (EDCs) in river water and wastewater. The experimental conditions affecting the SBSE-LD performance were studied and are discussed in detail. Results from systematic assay revealed that a 100-mL water sample, stir bars coated with 47?μL PDMS, an extraction time of 14?h (at 900?rpm), 5?% MeOH as modifier and 10?% NaCl resulted in the best analytical recovery of all the target compounds studied. Use of 1:1 ACN-MeOH as back-extraction solvent and two successive sonication steps, each for 5?min, resulted in the best performance for monitoring EDCs in water matrices. The method detection limits for most of the target compounds were very good- ≤?2?ng?L(-1) and ≤10?ng?L(-1) for river water and wastewater effluents respectively. Experimental recovery for all the compounds was >70?%, with the exception of simazine for which recovery from the matrix was 65?%. Signal enhancement observed for a few of the compounds in wastewater effluents was managed by use of matrix-matched standards and different injection liners. The method was successfully used for analysis of river water samples from Henares River (Spain) and wastewater effluent samples from wastewater-treatment plants (WWTP). Eleven of the 25 compounds studied were detected in both river water and wastewater effluents. Terbutylazine and methoxychlor were detected in almost all the river water and effluent samples; amounts varied between 37-58.5?ng?L(-1) and 15.2-46.8?ng?L(-1), respectively. This method was shown enable reliable, effective, and sensitive monitoring of chlorinated EDCs at nanogram levels in surface water and wastewater effluent.     

Determination of phenols in lake and ground water samples by stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry

A simple and inexpensive method for sorptive extraction of phenols from water samples is presented. A polydimethyl siloxane (PDMS) stir bar (Twister) is used as an extraction medium for derivatized phenols, which is thermally desorbed and analyzed by gas chromatography-mass spectrometry (GC-MS). Its performance was illustrated and evaluated for the enrichment of microg l(-1) to ng l(-1) of phenol and selected chlorophenols in water samples. The method showed good linearity, recoveries and blank levels, as well as advantages such as sensitivity, simplicity, low cost and high feasibility, being successfully applied for the analysis of phenolic compounds in natural water samples.     

Coupling of stir bar sorptive extraction with single photon ionization mass spectrometry for determination of volatile organic compounds in water

A home-made stir bar sorptive extraction (SBSE) apparatus was combined to a single photon ionization time-of-flight mass spectrometer (SPI-TOFMS) for rapid and sensitive determination of trace volatile organic compounds (VOCs) in water. The home-made SBSE bar, low-cost and disposable, was used for VOCs extraction. A thermal desorption (TD) device was designed to desorb the analytes from the SBSE bar, and a high throughput interface was developed to transfer the analytes into the ionization chamber of the SPI-TOFMS. The combination of large extraction volume of SBSE bar, and the direct measurement power of SPI-TOFMS enable a short analysis time for VOCs in water with high sensitivity, for example the limits of detection (LODs) were in the range of 7.4-11.1 ng L(-1) for benzene, toluene, and p-xylene (BTX) within 15 min. BTX aqueous solutions were chosen to demonstrate the quantitative capability, the linear range was from 0.05 to 100 μg L(-1) and the correlation coefficients were better than 0.996. The proposed method was successfully applied for the analysis of VOCs in urban river water.     

Determination of trace amounts of off-flavor compounds in drinking water by stir bar sorptive extraction and thermal desorption GC-MS.

A method for the determination of trace amounts of off-flavor compounds including 2-methylisoborneol, geosmin and 2,4,6-trichloroanisole in drinking water was developed using the stir bar sorptive extraction technique followed by thermal desorption-GC-MS analysis. The extraction conditions such as extraction mode, salt addition, extraction temperature, sample volume and extraction time were examined. Water samples (20, 40 and 60 ml) were extracted for 60-240 min at room temperature (25 degrees C) using stir bars with a length of 10 mm and coated with a 500 microm layer of polydimethylsiloxane. The extract was analyzed by thermal desorption-GC-MS in the selected ion monitoring mode. The method showed good linearity over the concentration range from 0.1 or 0.2 or 0.5 to 100 ng l(-1) for all the target analytes, and the correlation coefficients were greater than 0.9987. The detection limits ranged from 0.022 to 0.16 ng l(-1). The recoveries (89-109%) and precision (RSD: 0.80-3.7%) of the method were examined by analyzing raw water and tap water samples fortified at the 1 ng l(-1) level. The method was successfully applied to low-level samples (raw water and tap water).     

A rapid method of diagnosing pulmonary tuberculosis using stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry

A fast method for detection of tuberculostearic acid (TBSA) in sputum samples is described. The samples, obtained from patients with known or suspected pulmonary tuberculosis, were decontaminated and concentrated before being analyzed by stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry (SBSE-TD-GC-MS). Prior to extraction, the mycobacterial lipids were hydrolyzed and then derivatized with ethyl chloroformate to increase the sorption of the compounds by the polydimethylsiloxane (PDMS) stir bar coating. The limit of detection (LOD) is 0.2 ng ml(-1). Four sputum samples that were classified by direct microscopy as smear-positive or negative were analyzed by GC-MS. TBSA was detected at concentrations ranging from 0.47 to 2.3 ng ml(-1). The method is sufficiently sensitive to detect TBSA directly in clinical samples without the need to culture the organisms.     

Mercury speciation and analysis in drinking water by stir bar sorptive extraction with in situ propyl derivatization and thermal desorption-gas chromatography-mass spectrometry

A method for mercury analysis and speciation in drinking water was developed, which involved stir bar sorptive extraction (SBSE) with in situ propyl derivatization and thermal desorption (TD)-GC-MS. Ten millilitre of tap water or bottled water was used. After a stir bar, pH adjustment agent and derivatization reagent were added, SBSE was performed. Then, the stir bar was subjected to TD-GC-MS. The detection limits were 0.01 ng mL(-1) (ethylmercury; EtHg), 0.02 ng mL(-1) (methylmercury; MeHg), and 0.2 ng mL(-1) (Hg(II) and diethylmercury (DiEtHg)). The method showed good linearity and correlation coefficients. The average recoveries of mercury species (n=5) in water samples spiked with 0.5, 2.0, and 6.0 ng mL(-1) mercury species were 93.1-131.1% (RSD<11.5%), 90.1-106.4% (RSD<7.8%), and 94.2-109.6% (RSD<8.8%), respectively. The method enables the precise determination of standards and can be applied to the determination of mercury species in water samples.