Determination of polychlorinated biphenyls in water using dynamic hollow fiber liquid-phase microextraction and gas chromatography-mass spectrometry

The application of dynamic hollow fiber liquid-phase microextraction (dynamic HF-LPME) and gas chromatography-mass spectrometry (GC-MS) for the determination of trace amounts of polychlorinated biphenyls (PCBs) in water was investigated. The experimental parameters were optimized. Under the optimum conditions, the concentration enrichment factors for PCBs were from 718-fold to 840-fold. The calibration curves were linear over a range of 0.05-90mug/L, with a correlation coefficient (r(2)) of 0.9957-0.9979. The relative standard deviation (RSD) ranged from 3.4% to 5.8% for intra-day variation and from 4.1% to 7.3% for inter-day variation. The limits of detection (LODs, S/N=3:1) were in the range of 13-41ng/L. The recoveries for spiked water samples ranged from 85.9% to 92.0%.     

Analysis of PBDEs in soil,dust, spiked lake water,and human serum samples by hollow fiber-liquid phase microextraction combined with GC-ICP-MS

A novel method for the analysis of four polybrominated diphenyl ethers (PBDEs) in environmental and human serum samples based on hollow fiber-liquid phase microextraction (HF-LPME) followed by gas chromatography-inductively coupled plasma mass spectrometric (GC-ICP-MS) detection has been developed. The organic solvent in the porous hollow fiber was first dipped into the sample for extraction at a given time, and the retracted organic phase was introduced into the GC-ICP-MS for analysis. The addition of methanol has a strong effect on the HF-LPME extraction efficiency. Other significant parameters affecting the extraction efficiency of HF-LPME were also studied. HF-LPME was effective to isolate the analytes from the complex matrix. Under the optimized conditions, the detection limits of the proposed method varied from 15.2 to 40.5 ng/L. In general, the relative standard deviations (RSDs) were less than 10%. Good linearity was obtained with the correlation coefficients all better than 0.999. The proposed method is simple, quick, few microliters of organic solvent required, and is especially suitable for the analysis of the real sample with small amount available. The overall process of HF-LPME with GC-ICP-MS was applied successfully for the determination of polybrominated diphenyl ethers (PBDEs) in environmental and spiked human serum samples, and the results were satisfactory.     

Application of Double-Phase Liquid Phase Microextraction in the Determination of Partition Coefficients and Analysis of Pesticides in Water Samples

A simple and solvent-minimized sample preparation technique based on two-phase hollow fiber-protected liquid-phase microextraction has been developed and used for the determination of partition coefficient and analysis of selected pesticides in environmental water samples. The analysis was performed by gas chromatography–electron capture detector. Three pesticides namely hexaconazole, quinalphos, and methidathion were considered as target analytes. Extraction conditions such as solvent identity, salt concentration, stirring speed, extraction time, length of the hollow fiber, and volume of donor phase were optimized. The analytes were extracted from a donor phase (water sample) through 3 μL of an organic solvent immobilized in the pores of a porous polypropylene hollow fiber and then into the acceptor phase present inside the hollow fiber. Excellent extractions of the analytes were achieved under the optimized conditions, with relative standard deviations of 4.6–7.9%, correlation coefficients (r ²) of 0.9954–0.9986 and limits of detection of 3–7 ng L^?1. The proposed method provided good average enrichment factors of up to 250-fold. The partition coefficients of the analytes determined were found to be directly correlated with the enrichment factor. The present methodology also confirms the robustness of microextraction for monitoring trace levels of pesticides in environmental water samples.     

In situ derivatization and hollow fiber membrane microextraction for gas chromatographic determination of haloacetic acids in water

An alternative method for gas chromatographic determination of haloacetic acids (HAAs) in water using direct derivatization followed by hollow fiber membrane liquid-phase microextraction (HF-LPME) has been developed. The method has improved the sample preparation step according to the conventional US EPA Method 552.2 by combining the derivatization and the extraction into one step prior to determination by gas chromatography electron captured detector (GC-ECD). The HAAs were derivatized with acidic methanol into their methyl esters and simultaneously extracted with supported liquid hollow fiber membrane in headspace mode. The derivatization was attempted directly in water sample without sample evaporation. The HF-LPME was performed using 1-octanol as the extracting solvent at 55 °C for 60 min with 20% Na₂SO₄. The linear calibration curves were observed for the concentrations ranging from 1 to 300 μg L⁻¹ with the correlation coefficients (R²) being greater than 0.99. The method detection limits of most analytes were below 1 μg L⁻¹ except DCAA and MCAA that were 2 and 18 μg L⁻¹, respectively. The recoveries from spiked concentration ranged from 97 to 109% with %R.S.D. less than 12%. The method was applied for determination of HAAs in drinking water and tap water samples. The method offers an easy one step high sample throughput sample preparation for gas chromatographic determination of haloacetic acids as well as other contaminants in water.     

Multi-residue determination of organophosphorus and organochlorine pesticides in environmental samples using solid-phase extraction with cigarette filter followed by gas chromatography-mass spectrometry

A solid‐phase extraction (SPE) method was developed to extract 14 pesticides simultaneously from environment samples using cigarette filter as the sorbent before gas chromatography‐mass spectrometry (GC‐MS) analysis. Parameters influencing the extraction efficiency, such as the sample loading flow rate, eluent and elution volume, were optimized. The optimum sample loading rate was 3 mL/min, and the retained compounds were eluted with 6 mL of eluent at 1 mL/min under vacuum. Good linearity was obtained for all the 14 pesticides (r²>0.99) from 0.1 to 20 μg/L for water and from 2 to 400 μg/kg for soil samples. The detection limits (signal‐to‐noise=3) of the proposed method ranged from 0.01 to 0.20 μg/L for water samples and from 0.42 to 6.95 μg/kg for soil samples. The developed method was successfully applied for determination of the analytes in real environmental samples, and the mean recoveries ranged from 76.4 to 103.7% for water samples and from 79.9 to 105.3% for soil samples with the precisions (relative standard deviation) between 2.0 and 13.6%.     

Analysis of polycyclic aromatic hydrocarbons in water and beverages using membrane-assisted solvent extraction in combination with large volume injection-gas chromatography-mass spectrometric detection

Membrane-assisted solvent extraction (MASE) in combination with large volume injection-gas chromatography-mass spectrometry (LVI-GC-MS) was applied for the determination of 16 polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. The MASE conditions were optimized for achieving high enrichment of the analytes from aqueous samples, in terms of extraction conditions (shaking speed, extraction temperature and time), extraction solvent and composition (ionic strength, sample pH and presence of organic solvent). Parameters like linearity and reproducibility of the procedure were determined. The extraction efficiency was above 65% for all the analytes and the relative standard deviation (RSD) for five consecutive extractions ranged from 6 to 18%. At optimized conditions detection limits at the ng/L level were achieved. The effectiveness of the method was tested by analyzing real samples, such as river water, apple juice, red wine and milk.     

Orthogonal array design for the optimization of hollow fiber protected liquid-phase microextraction of salicylates from environmental waters

In the present study, a three phase-based hollow fiber protected liquid-phase microextraction (HF-LPME) method combined with high-performance liquid chromatography (HPLC) for the determination of salicylates in environmental waters was developed. The HF-LPME procedure was optimized by an L₁₆(4⁵) orthogonal array experimental design (OAD) with five factors at four levels. Under the optimal extraction condition (pHs of donor and receiving phases of 3.0 and 6.2, respectively, extraction time of 45 min, stirring speed of 1000 rpm, and salt addition of 20% (w/v)), salicylates could be determined in a linear range from 0.025 to 1.0 μg mL⁻¹ with a good correlation (r² > 0.9930). The limits of detection (LODs) ranged between 0.6 ng mL⁻¹ and 1.2 ng mL⁻¹ for the target analytes. The relative standard deviations (RSDs) of intra-day and inter-day were in the range of 0.64–14.58% and 0.16–15.45%, respectively. This procedure afforded a convenient, sensitive, accurate and cost-saving operation with high extraction efficiency for the model analytes. The method was applied satisfactorily to the determination of salicylates in two environmental waters.     

Determination of sulfonamide compounds in sewage and river by mixed hemimicelles solid-phase extraction prior to liquid chromatography-spectrophotometry

Mixed hemimicelles-based solid-phase extraction was investigated for the preconcentration of five sulfonamides from environmental water samples prior to HPLC-spectrophotometry determination in this paper. A comparative study on the use of sodium dodecyl sulfate (SDS) coating gamma-alumina or octadecyltrimethylammonium bromide (OTMABr) and OTMABr coating silica as sorbent materials were presented. The five analytes (sulfadiazine (SDA), sulfathiazole (STA), sulfapyridine (SPD), sulfamethazine (SMZ) and sulfamethoxazole (SMX)) were quantitatively adsorbed on OTMABr-gamma-alumina and OTMABr-silica mixed hemimicelles, but OTMABr-gamma-alumina was not adopted because it worked at a high pH (around 10), instead, OTMABr-silica was selected to overcoming the pH restriction. The analytes retained on the cartridge were quantitatively desorbed with suitable amounts of methanol. Factors influencing the extraction efficiency, such as the amount of surfactant, pH of sample and breakthrough volume were discussed. The proposed method had been applied to determining the five sulfonamides in several environmental water samples and concentration factors of 300 and 600 for SDA and other four analytes were achieved, respectively. Detection limits obtained ranged between 0.15 and 0.35microg/L for this five sulfonamides under the optimized conditions. The accuracy of the method was evaluated by recovery measurements on spiked samples, and good recovery results (89-113%) with precision of 3-6% were achieved.     

Hollow-Fibre Liquid-Phase Microextraction for the Determination of Polycyclic Aromatic Hydrocarbons in Johannesburg Jukskei River, South Africa

A simple, rapid and environmentally friendly hollow-fibre liquid-phase microextraction (HF-LPME) technique was developed for the quantitative determination of polycyclic aromatic hydrocarbons (PAHs) in aqueous samples. GC-MS was then used as the method of analysis. The HF-LPME technique involves extraction of PAHs from a 20-mL sample containing 20 % acetonitrile as a modifier. The PAHs were extracted into a 5-cm hollow fibre filled with heptane as organic solvent. At a stirring speed and extraction time of 600 rpm and 30 min, respectively, the acceptor solvent was then collected to be analysed. Parameters that affect the extraction efficiency were optimised in order to achieve high enrichment of the analytes. In order to evaluate the practical applicability of the HF-LPME technique, the performance of the method was compared to solid-phase extraction using spiked deionised water and real water samples. The obtained concentration enrichment factors ranged from 48 to 95 for HF-LPME and 81–135 for SPE, depending on the individual PAH. The detection limit ranged from 23 to 95 ng L^?1 for HF-LPME and 20–52 ng L^?1 for SPE. Water samples from the Johannesburg area, South Africa, were analysed using both extraction methods and the results were in good agreement. The relative standard deviations were less than 12 % for both methods. In this comparison, SPE was found to give high concentration enrichment factors and recovery, whereas faster and cheaper analyses were achieved with HF-LPME. The concentration of PAHs found could be arranged in the following order: phenanthrene > acenaphthene > fluoranthene > naphthalene > pyrene.     

Comparison of two extraction methods for the determination of selective serotonin reuptake inhibitors in sewage sludge by hollow fiber liquid-phase microextraction

This paper presents two procedures for the determination of four selective serotonin reuptake inhibitors (citalopram, paroxetine, fluoxetine, and sertraline) and one metabolite (norfluoxetine) in sewage sludge utilizing three-phase hollow fiber liquid-phase microextraction (HF-LPME). First, direct HF-LPME was used for extraction, clean-up, and preconcentration. The pharmaceuticals were extracted from slurry samples into an organic phase and then back-extracted into an aqueous phase in the lumen of the hollow fiber. Second, a procedure combining pressurized hot water extraction and HF-LPME for clean-up and preconcentration was developed for the same analytes and matrix. The extracts were subsequently analyzed by liquid chromatography-mass spectrometry. For direct HF-LPME, limits of detection were between 1 and 12 ng g(-1) (dry weight) and the relative standard deviation (RSD) values were 3-12%. For the second method, limits of detection were approximately 6 ng g(-1) for all the compounds and RSD values were 8-12%. The methods were validated by comparison of results for the same samples. Sewage sludge from a Swedish wastewater treatment plant was analyzed by both methods; average concentrations were similar for citalopram, paroxetine, and fluoxetine with values of approximately 530, 40, and 200 ng g(-1) , respectively.     

Hollow-fibre liquid-phase microextraction: a simple and fast cleanup step used for PAHs determination in pine needles

A new, fast and simple cleanup procedure, based on hollow-fibre liquid-phase microextraction (HF-LPME) is described here, used for the determination of 13 polycyclic aromatic hydrocarbons (PAHs) in complex pine needle samples. Initially, pine needle samples were sonicated in a 20 mL aqueous solution having a 20% (v:v) acetone content and 5 mL of the sonicated liquid extract was then used for the HF-LPME cleanup step. Different experimental parameters (namely: type of organic solvent used as acceptor phase, effect and type of co-solvent, salt addition, sample agitation and sampling time) were controlled and optimized based on the response of GC-MS instrument under the SIM mode. Under the optimized experimental conditions found the typical chromatograms obtained revealed that despite the very complex matrix of pine needles the HF-LPME cleanup step greatly reduced if not eliminated the presence of interferents, resulting in chromatograms which contained very cleanly separated and readily evaluable PAH peaks. In addition, the proposed method was found to be linear in the concentration 10-2000 ng g⁻¹ for most target analytes and the limits of detection for a S/N = 3 ranged between 0.01 and 0.95 ng g⁻¹ (dry weight). Furthermore, the repeatability and reproducibility were also found good. Finally, the proposed method was applied for the analysis of real pine needle samples taken for different parts of the island of Crete.     

Magnetic Graphene Nanoparticles for the Preconcentration of Chloroacetanilide Herbicides from Water Samples Prior to Determination by GC-ECD

A highly sensitive method for the determination of the chloroacetanilide herbicides alachlor, acetochlor, pretilachlor, butachlor, and metolachlor in environmental water samples was developed. It is based on solid-phase extraction using magnetic graphene nanocomposite (G-Fe₃O₄) as the adsorbent, followed by gas chromatography with electron capture detection. This novel adsorbent showed a great adsorptive ability toward the analytes. The main experimental parameters such as the amount of G-Fe₃O₄, extraction time, ionic strength, the pH of the sample solution, and desorption conditions were optimized. Under the optimum conditions, the enrichment factors of the method for the analytes were in the range from 649 to 1078. A good linear response was achieved in the range of 0.2–20.0 ng mL^?1, with correlation coefficients (r) varying from 0.9964 to 0.9998. The limits of detection of the method ranged from 0.02 to 0.05 ng mL^?1 and the relative standard deviations were below 4.5%. The method was successfully applied to the determination of the herbicides in environmental water samples. Recoveries of the method for the analytes were in the range of 80.7–105.3%.     

Determination of selected pesticides in environmental water by employing liquid-phase microextraction and liquid chromatography–tandem mass spectrometry

An optimised extraction and cleanup method for the analysis of pesticide in natural water samples is presented. Sixteen pesticides of different polarity and from the different chemical classes (organophosphates, triazines, benzimidazoles, carbamates, carbamides, neonicotinoides, methylureas, phenylureas and benzohydrazides), most frequently used in Serbia, were selected for the analysis. Liquid-phase microextraction in a single hollow fibre (HF-LPME) has been applied for sample preparation. The concentrations of pesticides were determined using HPLC-MS/MS method with electrospray ionisation. The extraction behaviour and selection of the experimental conditions was predicted based on log D and pK _a values of targeted pesticides, which were calculated applying the computer software ACD/Labs PhysChem Suite v12. The influence of the donor pH and concentration of pesticides, organic phase composition as well as the extraction time on the extraction efficiency was investigated. Optimum extraction conditions were evaluated with respect to the investigated parameters of the extraction. The extraction method was validated for 10 out of 16 studied pesticides. Linear range of the pesticides was 0.1–5 μg L⁻¹ with the correlation coefficient from 0.991 to 0.9998, and the relative standard deviation for three standard measurements was between 0.2 and 11.8%. The limits of detections ranged from 0.026 to 0.237 μg L⁻¹ and the limits of quantifications from 0.094 to 0.793 μg L⁻¹. The optimised two-phase HF-LPME method was successfully applied for determination of moderately polar as well low-polar pesticides in the environmental water samples.     

Application of graphene for the SPE clean‐up of organophosphorus pesticides residues from apple juices

In this paper, an effective graphene‐based SPE clean‐up procedure coupled with GC–MS was developed for the determination of organophosphorus pesticide residues in apple juices. The apple juice samples were diluted with water and could be loaded onto the cartridge directly. Several parameters affecting the extraction efficiency were investigated, including the type of elution, washing solution, and sample pH. Under the optimized conditions, excellent limits of quantitation for the target analytes were found to be 0.15–1.18 ng/mL, and the average recoveries of the analytes at two spiked levels for real‐sample analysis ranged from 69.8 to 106.2% with RSDs less than 7.3%. Furthermore, the graphene‐based cartridges exhibited superior reusability for juice sample analysis. The proposed method is sensitive, simple, and cost saving, and provides a detection platform for the monitoring of pesticide residues.     

Determination of nonsteroidal antiinflammatory drugs in water samples using liquid chromatography coupled with diode-array detector and mass spectrometry

An analytical method for the determination of trace levels of six different nonsteroidal antiinflammatory drugs (NSAIDs) in water samples has been developed and validated. Environmentally relevant pharmaceuticals were chosen according to human consumption in Poland. Final analysis of the target compounds was performed by RP LC-diode-array detection-MS, whereas sample preparation included an SPE step. For this SPE step, a number of packing materials, such as LiChrolut RP-18, calixarene, Strata-X, BAKERBOND Narc-2, BAKERBOND Polar Plus, BAKERBOND styrene divinylbenzene-1, and Discovery DSC-18, were used, and their respective advantages and disadvantages in this study were discussed. The RP-18 phase was found to be the most retentive for all analytes. The detection limits for compounds in surface waters were varied from 0.005 for diflunisal to 0.095 microg/L for ibuprofen. The average recoveries of NSAIDs from the surface water samples ranged from 80 up to 103%. RSD value is relatively low (from 4% for fenoprofen up to 8% for ibuprofen). The performance of the method was tested with several environmental water samples.     

超高效液相色谱-三重四极杆质谱联用同时检测环境水体中22种典型药品及个人护理用品

应用超高效液相色谱-三重四极杆质谱联用仪(UPLC-MS/MS)建立了环境水体中22种典型药品及个人护理用品(pharmaceuticals and personal care products, PPCPs)的分析方法。通过对固相萃取柱、淋洗液、色谱流动相等的优化,确定以Oasis HLB小柱为固相萃取柱、甲醇为淋洗液、水(0.1%甲酸)-甲醇(7:3, v/v)为流动相进行水样预处理和色谱分离。在最优条件下,目标物在水中的回收率为73%~125%,相对标准偏差(RSDs)为8.8%~17.5%。各目标物的线性范围均为2~2000 μg/L,线性相关系数(R²)不小于0.997。该方法具有检出限低、回收率高等优点,经实际样品测试,适用于环境水体中22种典型PPCPs的同时检测,可为微量有机物引起的水环境风险评价和控制的相关研究提供支持。     

Determination of haloethers in water with dynamic hollow fiber liquid-phase microextraction using GC-FID and GC-ECD

Dynamic hollow fiber liquid-phase microextraction (HF-LPME) coupled with gas chromatography with flame ionization detection (GC-FID) and GC-electron capture detecion (GC-ECD) was used for quantification of toxic haloethers in lake water. The analytes were extracted from 5 ml of aqueous sample using 4 μl of organic solvent through a porous polypropylene hollow fiber. The effects on extraction performance of solvent selection, agitation rate, extraction time, extraction temperature, concentration of salt added and volumes of solvent for extraction and injection were optimized. The proposed method provided a good average enrichment factor of up to 231-fold, reasonable reproducibility ranging from 9 to 12% (n = 3), and good linearity (R² ≧ 0.9973) for spiked water samples. Method detection limits (MDLs) ranged from 0.55 to 4.30 μg/l for FID and 0.11-0.34 μg/l for ECD (n = 7).     

Validation of a liquid chromatography coupled with tandem mass spectrometry method for the determination of drugs in wastewater using a three‐phase solvent system

Pharmaceuticals constitute one of the most important emerging classes of environmental pollutants. A three‐phase solvent system of water, water containing 0.1% of formic acid and acetonitrile was successfully used to separate, by liquid chromatography with mass spectrometry (LC‐MS), polarity‐matched pharmaceuticals, that is, carbamazepine, clarithromycin, and erythromycin, as well as amoxicillin and metformin. Despite of polarity similarities, these pharmaceuticals were completely resolved in the analytical run time of 15 min. The optimized three‐phase solvent system based‐method was validated for the simultaneous analysis of six matched‐polarity pharmaceuticals in wastewater samples. Good linearity (coefficient of determination more than 0.993) and precision (relative standard deviation less than 15.66%) were achieved. Recovery of analytes from the wastewater was between 0.70 and 1.18. Limits of detections ranged from 0.0001 to 0.5114 µg/L. No significant matrix effect, evaluated by post extraction addition, was observed in the electrospray ionization (ESI) source. Then, this methodology has been successfully applied to environmental study of pharmaceutical residues occurring in influent and effluent wastewater samples, from the main wastewater treatment plant in Potenza (Basilicata, Southern Italy).     

Microwave-assisted phase-transfer catalysis for the rapid one-pot methylation and gas chromatographic determination of phenolics

Microwave-assisted phase-transfer catalysis (PTC) is reported for the first time, for the one-step extraction–derivatization–preconcentration and gas chromatographic determination of twenty phenols and ten phenolic acids. The well established phase-transfer catalytic methylation is largely accelerated when heating is replaced with the “greener” microwave irradiation. The overall procedure was thoroughly optimized and the analytes were determined by GC/MS. The method presented adequate analytical characteristics being more sensitive in analyzing phenols than phenolic acids. The limits of detection without any additional preconcentration steps (e.g. solvent evaporation) were adequate and ranged from 0.4 to 15.8 ng/mL while limits of quantitation were between 1.2 and 33.3 ng/mL. The method was applied to the determination of phenols, in spiked environmental samples and phenolic acids in aqueous infusions of commercially available pharmaceutical dry plants. The recoveries of fortified composite lake water samples and Mentha spicata aqueous infusions ranged from 89.3% to 117.3% for phenols and 93.3% to 115.2% for phenolic acids.     

Comparison of conventional hollow fiber based liquid phase microextraction and electromembrane extraction efficiencies for the extraction of ephedrine from biological fluids

In the present study, hollow fiber liquid phase microextraction (HF-LPME) based on pH gradient and electromembrane extraction (EME) coupled with high-performance liquid chromatography (HPLC) was compared for the extraction of ephedrine from biological samples. The influences of fundamental parameters affecting the extraction efficiency of ephedrine were studied and optimized for both methods. Under the optimized conditions, preconcentration factors of 120 and 35 for urine and 51 and 8 for human plasma were obtained using EME and HF-LPME, respectively. The calibration curves showed good linearity for urine and plasma samples by both methods with the coefficient of estimations higher than 0.98. The limits of detection were obtained 5 and 10 ng mL(-1) using EME and 60 and 200 ng mL(-1) by HF-LPME for urine and plasma samples respectively. The relative standard deviations of the analysis were found in the range of 5.2-8.6% (n=3). The results showed that in comparison with HF-LPME based on pH gradient, EME is a much more effective transport process, providing high extraction efficiencies in very short time.