Titanium wire-based SPE coupled with HPLC for the analysis of PAHs in water samples

Titanium wire-based solid phase extraction (SPE) is developed for the analysis of six different polycyclic aromatic hydrocarbons in water samples with coupling with high performance liquid chromatography. The adsorbent is a Ti wire on which TiO(2) nanotubes are first formed by anodization and then Au nanoparticles and n-octadecanethiol are modified. The surface composition and structure of the adsorbent were characterized in detail using field emission scanning electron microscope and Fourier transform infrared spectroscopy. The main parameters affecting the extraction efficiency, such as the volume of the organic modifier, extraction time, elution solvent, and desorption time were optimized. Good linearities ranging from 0.025 to 30 μg L(-1) with correlation coefficients (R(2)) ranging from 0.9964 to 0.9999 and low limits of detection were obtained in spiked water samples. Furthermore, this method was successfully applied in the analysis of real river water samples with recoveries in the range of 75.33-115.83% and relative standard deviations ranging from 4.85 to 10.77%. The developed SPE can be a particularly convenient means of sample pretreatment for environmental water samples.     

Subcritical water extraction and determination of nifedipine in pharmaceutical formulations

A rapid and simple continuous method for the extraction of nifedipine from tablets was developed by using pressurized hot water at 150 degrees C. This is the first time that subcritical water was applied to the extraction of low-polarity compounds in pharmaceutical analysis. The method is based on the increment in solubility of nifedipine in subcritical water. Extraction temperature and static and dynamic extraction time were optimized in order to reach quantitative extraction of the drug from the tablets. After extraction, the drug was determined by spectrophotometry by measuring absorbance at 338 nm. Accuracy and precision of the method were determined by analysis of 10 synthetic samples of pharmaceutical formulations prepared with common tablet excipients. Recovery was found to be 99.2% with a relative standard deviation of 1.9%, which indicates that the excipients of the formulation do not interfere in the determination. The method was applied to the determination of the drug content uniformity in tablets.     

Trace determination of organotin compounds in water,sediment and mussel samples by low-pressure gas chromatography coupled to tandem mass spectrometry

A fast method for the determination of eight organotin compounds (OTs), monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), tetrabutyltin (TeBT), monophenyltin (MPhT), diphenyltin (DPhT), triphenyltin (TPhT) and tetraphenyltin (TePhT), in water, sediments and mussels, was developed using low-pressure gas chromatography/tandem mass spectrometry (LPGC/MS/MS). The method is based on sodium diethyldithiocarbamate (DDTC) complexation of the ionic organotins, followed by extraction of the target matrices and derivatization by a Grignard reagent, as described in a previously published method for water samples. Solid-phase extraction was selected as extraction method from water samples after comparison with liquid-liquid extraction, but extraction of the OTs from sediment and mussel samples was performed using toluene. Matrix-matched calibration standards were used to minimize matrix effects. The analytical process was validated by the analysis of spiked blank samples. Performance characteristics such as linearity, detection limit (LOD), quantitation limit (LOQ), precision, and recovery were determined. Recoveries of OTs in spiked matrices ranged from 86-108% in water and from 78-110% in sediments and mussels, with precision values lower than 18%. Detection limits ranged from 0.1-9.6 ng L(-1) in water, and 0.03-6.10 microg kg(-1) in the other matrices. The present implementation of LPGC rather than conventional capillary GC permitted use of large-volume injection and reduced analysis time by a factor of two. The proposed methodology was applied to the determination of OTs in real samples of water, marine sediments and mussels from the west coast of the Mediterranean Sea (Spain).     

Determination of decabromodiphenyl ether in water samples by single-drop microextraction and RP-HPLC

This paper describes the development of a new method using single-drop microextraction (SDME) and RP-HPLC for the determination of decabromodiphenyl ether (BDE-209) in water samples. The effects of SDME parameters such as extraction solvent, microdrop volume, extraction time, stirring speed, salt concentration, and sample pH on the extraction performance are investigated. Under optimal extraction conditions (extraction solvent, toluene; solvent drop volume, 3.0 microL; extraction time, 15 min; stirring speed, 600 rpm; no addition of salt and change of sample pH), the calibration curve was drawn by plotting peak area against a series of BDE-209 concentrations (0.001-1 microg/mL) in aqueous solution; the correlation coefficient (r) was 0.9998. The limit of detection was 0.7 ng/mL. The enrichment factor was 10.6. The precision of this method was obtained by six successive analyses of a 100 ng/mL standard solution of BDE-209, and RSD was 4.8%. This method was successfully applied to the extraction of BDE-209 from tap and East Lake water samples with relative recoveries ranging from 92.5 to 102.8% and from 91.5 to 96.2%, respectively, and the relative standard deviations (n = 3) were 4.4 and 2.2%. The proposed method is acceptable for the analysis of BDE-209 in water samples.     

Analysis of trace levels of sulfonamides in surface water and soil samples by liquid chromatography-fluorescence

Methods are reported for determining six sulfonamides used as veterinary drugs in water and soil samples. Analytes are isolated from water samples by solid-phase extraction on HBL cartridges and pre-concentration factors of up to 250 were obtained. Soil samples are treated using microwave-assisted extraction of analytes with acetonitrile and further clean up by solid-phase extraction. Determination is carried out by high-performance liquid chromatography using fluorimetric detection with precolumn derivatization with fluorescamine. The separation of the derivatized sulfonamides is performed on an octadecyl column using binary gradient elution with acetate buffer/acetonitrile mixtures. For water analysis, the detection limits of the whole process are in the low nanogram per liter level and recovery rates range from 70 to 104%, with standard deviations 2-11%. For soil analysis, extraction efficiency is evaluated using three soil samples with different physicochemical characteristics. Recovery rates range from 60 to 98% and detection limits are between 1 and 6ngg(-1).     

Fast determination of β-endosulfan, α-hexachlorocyclohexane and pentachlorobenzene in the river water from northeast of China

A magnetic solid-phase extraction method for the preconcentration of three organochlorine pesticides (OCPs) from water samples has been proposed, based on magnetic phosphatidylcholine (MPC) as adsorbents. The extraction procedure was carried out in a single step by stirring the mixture of MPC and water samples. Subsequently, the MPC was collected by an external magnetic field without additional centrifugation or filtration. The analytes were desorbed from the MPC and finally analysed by gas chromatography–tandem mass spectrometry. The influence of various parameters on OCPs recoveries was studied. Results show that phosphatidylcholine amount and extraction time were critical in enhancing extraction performance, and the presence of humic acid was shown to significantly reduce the extraction efficiency. The limits of detection obtained were in the range of 0.1–0.15 ng L^?1. Recoveries of spiked water samples ranged from 76.2% to 101.5% with relative standard deviations varying from 3.8% to 7.7%. The proposed method was employed for analysis of pentachlorobenzene, α-hexachlorocyclohexane and β-endosulfan in the surface water from two rivers in northeast China.     

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).     

微波辅助提取-固相膜萃取测定水体沉积物中的甲基汞

利用微波辅助提取-固相膜萃取前处理技术分离富集水体沉积物中的甲基汞,固相膜萃取的前处理方法能够集富集和净化为一体,有效地去除基质的影响。方法的关键在于样品的萃取过程,萃取过程中既要保证样品中甲基汞的原来形态不被破坏和转化,又要保证其从样品中被充分萃取以达到稳定可靠的回收效果。通过微波辅助提取技术将水体沉积物中的甲基汞提取到溶液后,提取液通过0.01%的二乙基二硫代氨基甲酸钠改性后的C18固相萃取膜,选择性地将提取液中的甲基汞分离富集的同时净化。洗脱液再经过原子荧光光谱仪进行测定。实验条件考察了流动相、微波提取条件以及固相膜萃取条件对甲基汞的影响。在最优的实验条件下,对甲基汞的稳定性进行了研究,实验结果表明在4 ℃以及-15 ℃条件下贮存,甲基汞降解不显著。同时对沉积物实际样品和加标样品进行了分析,所得结果沉积物中甲基汞检出限为0.20 μg/kg,沉积物实际样品的加标回收率和相对标准偏差分别在71.3%～87.6%和2.00%~6.36%之间,实验结果令人满意。该方法萃取速度快、消耗溶剂少、萃取效率高,可以同时处理多个样品,节约能耗,绿色环保,符合现代监测分析的发展趋势,适用于分析测定水体沉积物中的甲基汞。     

Water stability of zeolite imidazolate framework 8 and application to porous membrane-protected micro-solid-phase extraction of polycyclic aromatic hydrocarbons from environmental water samples

Zeolite imidazolate framework 8 (ZIF-8) has permanent porosity, high surface area, hydrophobic property, open metal sites and remarkable water stability. These novel properties characterize the material as being different from other moisture sensitive metal-organic frameworks and endow ZIF-8 with the potential to extract trace analytes from environmental water samples. In the present study, ZIF-8 was synthesized and used as a sorbent for micro-solid-phase extraction of 6 polycyclic aromatic hydrocarbons (PAHs) from environmental water samples for the first time. Parameters influencing the extraction efficiency such as desorption time, extraction time, desorption solvent and salt concentration were investigated. Environmental water samples collected from a local lake were processed using this novel μ-SPE procedure. ZIF-8 proved to be a very efficient extraction sorbent for the extraction of trace analytes from water samples. The limits of detection from gas chromatography-mass spectrometric analysis of PAHs were 0.002-0.012 ng/ml. The linear ranges were 0.1-50 or 0.5-50 ng/ml. The relative standard deviations for five replicates of the extractions were in the range of 2.1-8.5%.     

Analysis of Six Phenolic Endocrine Disrupting Chemicals in Surface Water and Sediment

An efficient and reliable method based on gas chromatography–mass spectrometry (GC–MS) was developed for the extraction and analysis of six phenolic endocrine disrupting chemicals (EDCs), such as 4-nonylphenol (4-NP), nonylphenol-mono-ethoxylate (NP1EO), nonylphenol-di-ethoxylate (NP2EO), 4-tert-octylphenol (4-t-OP), bisphenol A (BPA) and 4-cumylphenol (4-CP) in surface water and sediment. The method was developed by using microwave-assisted extraction (MAE), solid phase extraction (SPE) and derivatization procedure. The MAE procedures were performed by optimizing three key process factors, consisted of extraction solvent, extraction temperature and holding time, affecting the extraction efficiency from sediment samples. For SPE, various parameters that may affect the recovery efficiency of water samples, such as SPE phase cartridge, elution solvent, as well as pH of water samples, were investigated. A series of derivatization conditions, such as derivatization reagent, reaction temperature and reaction time, were improved. The method achieved good repeatability and reproducibility with relative standard deviations <13% for all target EDCs in the both samples. Satisfactory recoveries for spiked water and sediment samples ranged from 85 to 101% and 74 to 105%, respectively. The limits of quantification varied from 0.20 (4-t-OP) to 11.50 ng L^?1 (NP2EO) and from 0.31 (4-t-OP) to 9.50 ng g^?1 dry weight (dw) (NP2EO) for water samples and sediment samples, respectively. The established method was successfully applied to the analysis of target EDCs in surface water and sediment samples collected from Caohai site of Dianchi Lake, China. The results showed that NP1EO, NP2EO and BPA were the three dominant phenolic EDCs in the site, reaching 114, 97 and 149 ng L^?1 in surface water, while 444, 186 and 178 ng g^?1 dw in surface sediment, respectively.     

超声辅助乳化液液微萃取-气相色谱-质谱分析水中的人工合成麝香

将超声辅助乳化与液液微萃取技术结合,建立了水体中人工合成麝香的气相色谱-质谱分析方法.优化前处理条件,包括萃取剂、萃取剂体积、萃取时间、萃取温度及离子强度的选择.结果表明:在10 mL水样中,加入50 μL氯苯作为萃取剂,4 0 MHz超声10 min,混匀,以4000 r/min离心10 min,移取下层有机相进样分析,效果佳.样品的富集倍数可达200倍,8种人工合成麝香在0.005～0.4 μg/L范围内线性关系良好,相关系数均大于0.994;检出限为0.3～0.5 ng/L;水样中加标回收率为96.2％～102.9％;相对标准偏差为2.3％～4.1％.本方法灵敏、快速、准确,可满足环境水样中痕量人工合成麝香监测的质控要求.     

Analyses of polychlorinated biphenyls in waters and wastewaters using vortex-assisted liquid-liquid microextraction and gas chromatography-mass spectrometry

A method was developed for viable and rapid determination of seven polychlorinated biphenyls (PCBs) in water samples with vortex-assisted liquid-liquid microextraction (VALLME) using gas chromatography-mass spectrometry (GC-MS). At first, the most suitable extraction solvent and extraction solvent volume were determined. Later, the parameters affecting the extraction efficiency such as vortex extraction time, rotational speed of the vortex, and ionic strength of the sample were optimized by using a 2(3) factorial experimental design. The optimized extraction conditions for 5 mL water sample were as follows: extractant solvent 200 μL of chloroform; vortex extraction time of 2 min at 3000 rpm; centrifugation 5 min at 4000 rpm, and no ionic strength. Under the optimum condition, limits of detection (LOD) ranged from 0.36 to 0.73 ng/L. Mean recoveries of PCBs from fortified water samples are 96% for three different fortification levels and RSDs of the recoveries are below 5%. The developed procedure was successfully applied to the determination of PCBs in real water and wastewater samples such as tap, well, surface, bottled waters, and municipal, treated municipal, and industrial wastewaters. The performance of the proposed method was compared with traditional liquid-liquid extraction (LLE) of real water samples and the results show that efficiency of proposed method is comparable to the LLE. However, the proposed method offers several advantages, i.e. reducing sample requirement for measurement of target compounds, less solvent consumption, and reducing the costs associated with solvent purchase and waste disposal. It is also viable, rapid, and easy to use for the analyses of PCBs in water samples by using GC-MS.     

Electromembrane extraction and preconcentration of carbendazim and thiabendazole in water samples before capillary electrophoresis analysis

Electromembrane extraction using a polypropylene hollow fiber impregnated with 1‐ethyl‐2‐nitrobenzene was evaluated for the extraction and preconcentration of the fungicides thiabendazole and carbendazim from water samples before capillary electrophoresis analysis. The composition of the supported liquid membrane, the HCl concentration in the acceptor solution, and the stirring rate (of the donor solution) were optimized using the one‐variable‐at‐a‐time method. In contrast, a face‐centered central composition design was used for optimization of voltage, extraction time, and concentration of HCl in the donor solution. After optimization, electromembrane extraction provided enrichment factors of 50 and 26 for thiabendazole and carbendazim that allowed us to achieve limits of detection of 1.1 and 2.3 μg/L, respectively. Repeatability (intraday precision) expressed as the relative standard deviation varied from 2.5 to 2.8%, while the interday precision ranged from 3.1 to 3.3%. The proposed method was applied for analysis of samples of tap and river water, and acceptable precision and accuracy were attained.     

单滴微萃取-气相色谱-质谱联用测定水中的硝基咪唑类药物

建立了单滴液相微萃取(SDME)与气相色谱-质谱(GC-MS)联用技术快速检测水中的硝基咪唑类药物,对影响萃取的因素(溶剂的种类及用量、萃取时间、萃取温度及搅拌子的搅拌速度)进行优化。优化的萃取条件为:溶剂为2.5μL正辛醇,温度为50℃,搅拌速度为600 r/min,时间为20 min。萃取后,微液滴转移至衍生化试管,于70℃水浴中衍生45 min,进样分析。该方法在水中的线性范围为0.5~400μg/L,线性相关系数良好(r0.998),检测限为0.16~0.57μg/L。加标自来水和湖水中的相对平均回收率为80.9%~103.6%,相对标准偏差为1.7%~9.0%。     

Preparation of monolithic fibers for the solid‐phase microextraction of chlorophenols in water samples

Monolithic fibers were synthesized and applied for the solid‐phase microextraction and determination of chlorophenols in environmental water samples by coupling with HPLC. The fibers were prepared by copolymerization of vinylimidazole and ethylene dimethacrylate as functional monomer and cross‐linker, respectively. The effect of the preparation conditions of monolithic fibers on the extraction efficiencies was investigated in detail. Several characteristic techniques, such as elemental analysis, infrared spectroscopy, mercury‐intrusion porosimetry, and SEM were used to characterize the monolithic material. The effect of the extraction parameters, including desorption solvent, extraction and desorption time, pH values, and ionic strength in sample matrix on the extraction performance was investigated thoroughly. Under the improved extraction conditions, the linear ranges of 2‐chlorophenol, 2,4‐dichlorophenol and pentachlorophenol were 1.0–200 μg/L and 2.0–200 μg/L for 2,4,6‐trichlorophenol. The detection limits (S/N = 3) were in the range of 0.16–0.45 μg/L, the RSDs for intraday and interday precisions were <7.0%. Finally, the proposed method was successfully used to detect different environmental water samples. The recoveries of spiked water samples were ranged from 90.0 to 115%. At the same time, satisfactory repeatability was achieved with RSDs < 9.0%.     

Trace Determination of Benzalkonium Chlorides in River and Wastewater by Capillary Electrophoresis following Solid‐Phase Extraction Coupled with Salting‐Out Extraction

Trace levels analysisbenzalkonium chlorides (BAKs) in river water and wastewater treatment plants (WWTP) effluents were determined by capillary electrophoresis (CE) following solid‐phase extraction (SPE) and salting‐out extraction. Salting‐out extraction using an appropriate ratio of sodium chloride (NaCl) and acetonitrile (ACN) mixed with concentrated SPE elutant was capable of providing more than 500‐fold enhancement in detection sensitivity. The ratios of ACN and NaCl for salting‐out extraction were investigated and optimized. Matrix interference was eliminated by salting‐out extraction. Limits of quantitation of BAK homologues were achieved at 0.1 μg/L in 250 mL water samples. Recoveries of BAKs in various spiked water samples ranged from 70% to 84% with relative standard deviation (RSD) less than 9%. Trace amounts of total BAKs were detected in river water and WWTP effluent samples ranging from 27 to 145 μg/L at the first time by CE.     

磁性氧化石墨烯固相萃取/高效液相色谱-串联质谱法测定环境水样中6种三嗪类除草剂残留

采用一步合成法制备磁性氧化石墨烯材料(GO-Fe_3O_4),将其用作磁性固相吸附剂对环境水样中的6种三嗪类除草剂进行萃取和富集,并与高效液相色谱-串联质谱法相结合进行测定。以扫描电镜和傅立叶红外光谱对合成材料进行了表征,并考察了GO-Fe_3O_4用量、萃取时间、水样的pH值及离子强度和解吸条件等因素对萃取效率的影响。6种三嗪类除草剂的检出限为0.1~1.0 ng/L,富集倍数可达616~902倍。将方法应用于苏州地区太湖水、运河水和护城河水等实际水样的分析,加标回收率为85.4%~117.6%,相对标准偏差为1.2%~10.0%。该方法操作简单快速,富集倍数较高,检出限低,可用于水样中痕量三嗪类除草剂残留的检测。     

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。     

Field analysis of benzene, toluene, ethylbenzene and xylene in water by portable gas chromatography-microflame ionization detector combined with headspace solid-phase microextraction

In this work, portable gas chromatography-microflame ionization detection (portable GC-μFID) coupled to headspace solid-phase microextraction (HS-SPME) was developed for the field analysis of benzene, toluene, ethylbenzene and xylene (BTEX) in water samples. The HS-SPME parameters such as fiber coating, extraction times, stirring rate, the ratio of headspace volume to sample volume, and sodium chloride concentration were studied. A 65 μm poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB) SPME fiber, 900 rpm, 3.0 ml of headspace (1.0 ml water sample in 4.0 ml vial), and 35% sodium chloride concentration (w/v) were respectively chosen for the best extraction response. An extraction time of 1.0 min was enough to extract BTEX in water samples. The relative standard deviation (R.S.D.) for the procedure varied from 5.4% to 8.3%. The method detection limits (MDLs) found were lower than 1.5 μg/l, which was enough sensitive to detect the BTEX in water samples. The optimized method was applied to the field analysis of BTEX in wastewater samples. These experiment results show that portable GC-μFID combined with HS-SPME is a rapid, simple and effective tool for field analysis of BTEX in water samples.     

Implementation of solid-phase microextraction with micellar desorption method for priority phenolic compound determination in natural waters

Eleven phenolic compounds considered by the Environmental Protection Agency to be priority pollutants are extracted and determined in different water samples. The method involves the extraction and clean-up step of target compounds by solid-phase microextraction and micellar desorption (SPME-MD) and a second step of determination by liquid chromatography with diode array detection. Different fibers and surfactants are evaluated for the analysis of these target analytes in water samples. In the optimum conditions for the SPME process, recoveries for the target compounds are between 80% and 109%; relative standard deviations are lower than 10%, and detection limits are in the range 0.3-3.5 ng/mL. The main advantages of this method are the combination of time and efficiency, safety, and an environmentally friendly process for sample extraction prior to instrumental determination. This demonstrates that SPME-MD can be used as an alternative to traditional methods for the extraction and determination of priority phenolic compounds in natural waters from different origins.