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.     

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.     

Determination of parabens in house dust by pressurised hot water extraction followed by stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry

This study describes the development of a new method for determining p-hydroxybenzoic esters (parabens) in house dust. This optimised method was based on the pressurised hot water extraction (PHWE) of house dust, followed by the acetylation of the extracted parabens, stir bar sorptive extraction (SBSE) with a polydimethylsiloxane stir bar, and finally analysis using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS). The combination of SBSE and PHWE allows the analytes to be preconcentrated and extracted from the aqueous extract in a single step with minimal manipulation of the sample. Furthermore the in situ acetylation of parabens prior to SBSE improved their extraction efficiency and their GC-MS signal. The method showed recoveries of between 40 and 80%, good linearity, repeatability and reproducibility (<10% RSD, at 100 ng g(-1), n=5), low limits of detection (from 1.0 ng g(-1) for propyl paraben to 2.1 ng g(-1) for methyl paraben) and quantification (from 3.3 ng g(-1) for propyl paraben to 8.5 ng g(-1) for methyl paraben). The proposed method was applied to the analysis of house dust samples. All the target parabens were found in the samples. Methyl and propyl parabens were the most abundant, with concentrations up to 2440 ng g(-1) and 910 ng g(-1), respectively. The high levels of parabens found in the samples confirm the importance of determining organic contaminants in indoor environments.     

Sequential stir bar sorptive extraction for uniform enrichment of trace amounts of organic pollutants in water samples

A novel extraction procedure for stir bar sorptive extraction (SBSE) termed sequential SBSE was developed. Compared to conventional SBSE, sequential SBSE provides more uniform enrichment over the entire polarity/volatility range for organic pollutants at ultra-trace levels in water. Sequential SBSE consists of a SBSE performed sequentially on a 5-mL sample first without modifier using one stir bar, then on the same sample after addition of 30% NaCl using a second stir bar. The first extraction with unmodified sample is mainly targeting solutes with high Kow (logKow>4.0), the second extraction with modified sample solution (containing 30% NaCl) is targeting solutes with low and medium Kow (logKow<4.0). After extraction the two stir bars are placed in a single glass desorption liner and are simultaneously desorbed. The desorbed compounds were analyzed by thermal desorption and gas chromatography-mass spectrometry (TD-GC-MS). Recovery of model compounds consisting of 80 pesticides (organochlorine, carbamate, organophosphorus, pyrethroid, and others) for sequential SBSE was evaluated as a function of logKow (1.70-8.35). The recovery using sequential SBSE was compared with those of conventional SBSE with or without salt addition (30% NaCl). The sequential approach provided very good recovery in the range of 82-113% for most of the solutes, and recovery less than 80% for only five solutes with low Kow (logKow<2.5), while conventional approaches (with or without salt addition) showed less than 80% recovery for 23 and 41 solutes, respectively. The method showed good linearity (r2>0.9900) and high sensitivity (limit of detection: <10ngL(-1)) for most of the model compounds even with the scan mode in the MS. The method was successfully applied to screening of pesticides at ngL(-1) level in river water samples.     

大体积搅拌棒吸附萃取技术与热脱附-气相色谱-质谱法测定地表水中多环芳烃

基于搅拌棒吸附萃取(SBSE)技术建立了气相色谱-质谱测定地表水中16种多环芳烃(PAHs)的分析方法。该法采用多搅拌吸附棒同时富集,依次热脱附冷聚焦后进样的方式有效解决了搅拌棒吸附时间长、富集水样体积小等问题。优化后的结果表明,在0.2~10 ng/L范围内(萘为0.5~10 ng/L范围),16种PAHs的线性关系良好,相关系数(r)均0.99,方法检出限(MDL)为0.03~0.20 ng/L(萘为0.50 ng/L)。用该方法对钱塘江流域地表水进行测定,共检测出11种PAHs,含量为0.13~1.57 ng/L,不同添加水平下的加标回收率为75.6%~108.9%。该法可应用于地表水样品中该类物质的超痕量检测。     

Comparison of Stir Bar Sorptive Extraction and Solid Phase Extraction as Enrichment Techniques in Combination with Column Liquid Chromatography for the Determination of Polycyclic Aromatic Hydrocarbons in Water Samples

The commonly used solid-phase extraction (SPE) was compared with the recently developed stir bar sorptive extraction (SBSE) to determine EPA-PAHs from precipitation water samples. SPE was performed using C18 PAH-filled cartridges; magnetic stirring rods 10 mm long and coated with 0.5 mm (24 µL) polydimethylsiloxane were used for SBSE. Determination was performed by high performance liquid chromatography and fluorescence detection. The investigations were performed at a concentration level of 30 ng/L, adjusted to actual PAH concentration levels of precipitation water. The recoveries ranged between 54% (SBSE) and 20% (SPE) respectively and about 100%, while the standard deviation ( n = 5) varied in the range of 4.7-13.5% (SBSE) and 3.6-16.9% (SPE) except for the more volatile compounds acenaphthene and fluorene. The detection limits calculated were between 0.4 and 5.0 ng/L. Both techniques were applied to study the PAH contents of precipitation water of several polluted sites in the city of Halle (Saxony-Anhalt, Germany). The advantages and disadvantages of the methods used are discussed.     

聚酰亚胺固相萃取搅拌棒的制备及其在环境水中酚类的分析应用

利用相转换法制备了聚酰亚胺吸附萃取搅拌棒,用5种有机酚作为评价标样,并与现有商品化吸附萃取搅拌棒进行比较。优化了萃取搅拌速度、溶液离子强度、萃取温度、萃取时间以及热解析温度和时间。在最佳实验条件下,100 mL 样品,30% NaCl,在25℃下,经活化5 min 后的聚酰亚胺吸附搅拌棒萃取30 min (800 r/ min),然后300℃热解析4 min,使目标物脱附,再进行色谱分析。目标物在大于两个数量级浓度范围内具有良好的线性(R≥0.9995),定量限(LOQ,S/ N=10)为0.028~0.123μg/ L,重复性为1.6%~9.7%。将SBSE 与气相色谱-质谱联用,对海水、自来水和污水中的酚类进行定性与定量分析,结果表明,聚酰亚胺吸附萃取搅拌棒具有良好的选择性,最高热解析温度350℃,在分析水中痕量极性化合物领域具有广阔应用前景。     

Analysis of off-flavors in the aquatic environment by stir bar sorptive extraction–thermal desorption–capillary GC/MS/olfactometry

The off-flavor compounds 2-methylisoborneol (MIB), geosmin, 2,4,6-trichloroanisole, 2,3,6-trichloroanisole, 2,3,4-trichloroanisole, and 2,4,6-tribromoanisole were analyzed in water samples by stir bar sorptive extraction (SBSE) followed by on-line thermal desorption (TD) capillary GC/MS. Quantification was performed using the MS in the single-ion-monitoring mode (SIM) with 2,4,6-trichloroanisole-D(5 )as internal standard. Quantification limits are 0.1-0.2 ng L(-1) for the haloanisoles, 0.5 ng L(-1) for geosmin, and 1 ng L(-1) for MIB. The relative standard deviations at the quantification limit ranged from 7 to 14.6%. SBSE recovery was evaluated by spiking real water samples and varied from 87 to 117%. More than twenty samples per day can be analyzed by SBSE-TD-capillary GC-MS. The same technique in combination with olfactometry was used to elucidate unknown odorous compounds in 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.     

Analysis of 51 persistent organic pollutants in soil by means of ultrasonic solvent extraction and stir bar sorptive extraction GC-MS

A novel method based on ultrasonic solvent extraction and stir bar sorptive extraction (SBSE) for the analysis of 51 persistent organic pollutants including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and polybrominated diphenylethers (PBDEs) in soil samples was developed. The different parameters that affect both the extraction of analytes from the soil samples, such as solvent selection, solvent volume, mass of soil, and extraction time, and the partitioning from the solvent/water mixture to the PDMS were studied. The final selected conditions consisted of the extraction of 1 g of soil with 15 mL methanol by sonication for 30 min. The methanol extract was mixed with 85 mL of Milli-Q water and extracted by means of SBSE for 14 h at 900 rpm. The stir bars were analyzed by thermal desorption-GC-mass spectometry (TD-GC-MS). The effects of the matrix on the recovery of the various pollutants under the developed method were studied using two soils with very different physicochemical properties. Method sensitivity, linearity, repeatability, and reproducibility were also studied. Validation and accuracy of the method were conducted by analyzing two commercial certified reference materials (CRMs). The main advantage of this method resides in the fact that a small amount of a nontoxic solvent (methanol) is needed for the extraction of only 1 g of solid sample allowing LODs ranging from 0.01 to 2.0 microg/kg. Repeatability and reproducibility variations were lower than 20% for all investigated compounds. Results of the CRMs verify the high accuracy of this method.     

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.     

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).     

应用搅拌棒吸附萃取-热脱附-气质联用技术分析人工唾液捕集吸收的卷烟主流烟气成分

采用人工唾液捕集卷烟主流烟气,应用搅拌棒吸附萃取法(SBSE)提取其中的化学成分,利用热脱附(TD)-气相色谱-质谱(GC-MS)进行分析。对脱附温度、脱附时间、冷阱温度、萃取时间及NaCl加入量等影响因素进行考察,获得优化的实验条件。在优化条件下,同一样品的6次测定所得44个组分的峰面积的相对标准偏差(RSD)平均值小于10%,说明所建方法重现性较好。应用本方法分析某品牌卷烟烟气成分的结果表明:SBSE-TD-GC-MS联用技术可用于人工唾液捕集吸收的烟气化学成分的快速分析测定。     

Optimized method for the determination of 25 polychlorinated biphenyls in water samples using stir bar sorptive extraction followed by thermodesorption-gas chromatography/mass spectrometry

An optimized method using stir bar sorptive extraction (SBSE) for the determination of 25 polychlorinated biphenyls (PCBs) from water samples among them three of the most toxic coplanar PCBs (PCB 77, PCB 126 and PCB 169) was developed. Since the investigated PCBs comprise all steps of chlorination (from PCB 1 as monochlorobiphenyl to PCB 209 as decachlorobiphenyl) the results should be representative for the total class of the 209 PCB congeners. For 8 ml spiked water samples with 2 ml methanol addition and 2 h exposure time of stir bars recoveries between 28% (PCB 209) and 93% (PCB 1, PCB 52, PCB 77) were found. Detection limits between 0.05 ng/l and 0.15 ng/l were calculated for the combination of SBSE and thermodesorption-GC/MS. The procedure was applied to the investigation of groundwater and river water samples from the industrial region of Bitterfeld northern Leipzig, Germany.     

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.     

固相萃取搅拌棒萃取-气相色谱分析海水中的多环芳烃

利用固相萃取搅拌棒（SBSE）萃取海水中的多环芳烃，然后用热解吸脱附-气相色谱分析。研究了萃取时间、添加NaCl浓度对萃取效率的影响。实验结果表明，SBSE方法对16种多环芳烃的萃取回收率分别在33．5％～122．4％之间；对标准样品的检出限为2．74-13．5ng／L；方法RSD为3．8％～13．1％。用此方法测定了大连海岸海水中的多环芳烃含量。     

Determination of trace polychlorinated biphenyls and organochlorine pesticides in water samples through large‐volume stir bar sorptive extraction method with thermal desorption gas chromatography

A fast and sensitive analytical method based on stir bar sorptive extraction technology with gas chromatography and mass spectrometry was developed to simultaneously analyze 18 kinds of polychlorinated biphenyls and 20 kinds of organochlorine pesticides in aqueous samples. A long adsorption time and small sample volume, which are problems encountered in conventional methods of stir bar sorptive extraction, were effectively solved by simultaneously using multiple stir bars for enrichment with sequential cryofocusing and merged injection. Optimized results showed good linear coefficients in the range of 10–500 ng/L and the method detection limits of 0.12–2.07 ng/L for polychlorinated biphenyls and organochlorine pesticides. The recovery ratios of the spiked samples at different concentrations were between 64.7 and 111.0%, and their relative standard deviations ranged from 0.9 to 17.6%. Four types of the studied compounds were determined in Qiantang River water samples, and their contents were between 0.82 and 5.00 ng/L.     

Measurement of perchlorate in water by use of an 18O-enriched isotopic standard and ion chromatography with mass spectrometric detection

A novel analytical method has been developed for the determination of 4-tert.-octylphenol (OP) and 4-nonylphenol (NP) in laboratory animal feed samples, which involves stir bar sorptive extraction (SBSE) followed by liquid desorption (LD) and column-switching liquid chromatography-mass spectrometry (CS-LC-MS) with solid-phase extraction (SPE). The method required correction by stable isotopically labeled surrogate standards, deuterium 4-tert.-octylphenol (OP-d) and [2H5] 4-(1-methyl)octylphenol (m-OP-d5). A feed sample was homogenized with methanol by ultrasonication. After centrifugation, the supernatant was subjected to extraction for 120 min at room temperature (25 degrees C) using a stir bar coated with polydimethylsiloxane. After the extraction, the analyte was desorbed from the stir bar by LD using acetonitrile. Then, the liquid sample was analyzed by CS-LC-MS with SPE. The average recoveries from laboratory feed samples spiked with OP and NP at 20 ng g(-1) were 99.5 and 103.8%, respectively, with correction using the added surrogate standards. The limits of quantification were 1 ng g(-1) for OP and 5 ng g(-1) for NP in feed sample. The measurement of OP and NP in commercial laboratory animal feed samples resulted in the detection of sub ng g(-1) NP     

Stir bar sorptive extraction and high-performance liquid chromatography-fluorescence detection for the determination of polycyclic aromatic hydrocarbons in Mate teas

A simple procedure based on stir bar sorptive extraction (SBSE) and high-performance liquid chromatography-fluorescence detection (HPLC-FLD) is presented for the determination of 15 polycyclic aromatic hydrocarbons (PAHs) in herbal tea prepared with Mate leaves (Ilex paraguariensis St. Hil.). The influence of methanol and salt addition to the samples, the extraction time, the desorption time and the number of desorption steps, as well as the matrix effect, were investigated. Once the SBSE method was optimised (10 mL of Mate tea, 2h extraction at room temperature followed by 15 min desorption in 160 microL of an acetonitrile (ACN)-water mixture), analytical parameters such as repeatability (< or = 10.1%), linearity (r2 > or = 0.996), limit of detection (LOD, 0.1-8.9 ng L(-1) ), limit of quantitation (LOQ, 0.3-29.7 ng L(-1) and absolute recovery (24.2-87.0%) were determined. For calibration purposes, a reference sample was firstly obtained by removing the analytes originally present in the lowest contaminated Mate tea studied (via SBSE procedure) and then spiked at 1-1200 ng L(-1)range. The proposed methodology proved to be very convenient and effective, and was successfully applied to the analysis of 11 Mate tea samples commercialised in Brazil. The results of the commercial Mate tea samples found by the SBSE approach were compared with those obtained by liquid-liquid extraction (LLE), showing good agreement.     

pH-resistant titania hybrid organic-inorganic coating for stir bar sorptive extraction of drugs of abuse in urine samples followed by high performance liquid chromatography-ultraviolet visible detection

An organic-inorganic hybrid titania-hydroxy-terminated silicone oil (titania-OH-TSO) stir bar coating was prepared by sol-gel method. The extraction performance of titania-OH-TSO coated stir bar was evaluated and compared with poly(dimethysiloxane) (PDMS), poly(dimethysiloxane)-divinylbenzene (PDMS-DVB), poly(dimethysiloxane)-β-cyclodextrin (PDMS-β-CD) and C(18) coated stir bar with five polar drugs of abuse including amphetamine (PA), methamphetamine (MA), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA) and ketamine (Ke) as the model analytes. The experimental results revealed that the titania-OH-TSO coated stir bar exhibited highly pH-resistant ability, good preparation reproducibility, superior selectivity and high extraction efficiency for the target compounds. Based on this fact, a new method of titania-OH-TSO coated stir bar sorptive extraction (SBSE) combined with high performance liquid chromatography (HPLC)-ultraviolet visible (UV) detection was developed for the analysis of five drugs of abuse in urine samples. The factors affecting the extraction efficiency of SBSE such as sample pH, desorption solvent, sample volume, extraction time, desorption time, stirring rate and ionic strength were investigated and the optimal extraction conditions were established. Under the optimized conditions, the limits of detection (LODs) for titania-OH-TSO coated SBSE-HPLC-UV determination of five polar drugs of abuse were in the range of 2.3-9.1 μg/L with relative standard deviations (RSDs) ranging from 7.3 to 8.9% (c=300 μg/L, n=6), and all of the target compounds exhibited good linearity over a concentration range of 30-3000 μg/L. The developed method was applied to the determination of amphetamines and Ke in urine samples of drug abusers with satisfactory results.