Development of a solid-phase extraction method for the determination of polychlorinated biphenyls in water

Polychlorinated biphenyls (PCBs) in water were extracted with a rebuilt extraction unit using 47 mm C18 solid-phase extraction (SPE) disks. Three types of disks (SPEC, ENVI and Empore) were investigated for the extraction of seven PCBs from 11 reagent water spiked at two concentration levels (20 and 1000 ng/l). The Empore disks produced the best analyte recoveries (91-107% with R.S.D. of 1-8%) at the low concentration level and displayed no leaking tendency. Empore disks were therefore considered superior to ENVI and SPEC disks for the conditions outlined in this work. The obtained extracts were dried and purified in an additional clean-up step using custom-made columns containing Florisil and Na2SO4. For water containing large amounts of organic matter, a pre-filtration was included. Final analysis was carried out on a dual-column GC-electron-capture detection system with on-column injection. The optimised extraction method, including clean-up, was less time-consuming and used less hazardous organic solvents than conventional liquid-liquid extraction (LLE) methods. Recoveries were 92-102% with R.S.D. of 3-8%.     

Analysis of polychlorinated biphenyls in aqueous samples by microwave-assisted headspace solid-phase microextraction

The hyphenated technique namely microwave-assisted headspace solid-phase microextraction (MA-HS-SPME) was developed and studied for the simultaneous extraction/enrichment of polychlorinated biphenyls (PCBs) in aqueous samples prior to the quantification by gas chromatography (GC). The PCBs in aqueous media are extracted onto a solid-phase micro fibre via the headspace with the aid of microwave irradiation. The optimum conditions for obtaining extraction efficiency, such as the extraction time, addition of salts, addition of methanol, ratio of sample to headspace volume, and the desorption parameters were investigated. Experimental results indicated that the proposed MA-HS-SPME method attained the best extraction efficiency under the optimized conditions, i.e., irradiation of extraction solution (20 ml aqueous sample in 40 ml headspace vial with no additions of salt and methanol) under 30 W microwave power for 15 cycles (1 min power on and 3 min power off of each cycle). Desorption at 270 degrees C for 3 min provided the best detection results. The detection limit obtained were between 0.27 and 1.34 ng/l. The correlation coefficient for the linear dynamic range from 1 to 80 ng/l exceeded 0.99 for 18 PCBs.     

微波辅助萃取-气相色谱测定土壤中多氯联苯

建立了微波辅助萃取-气相色谱-微电子捕获检测土壤样品中6种多氯联苯(pcb28, pcb52, pcb101, pcb138, pcb153和pcb180)的方法. 确定了以V(20 mL丙酮):V(正己烷)＝1:1混合溶剂作萃取剂, 萃取温度110 ℃, 仪器功率800 W, 微波萃取5 min的样品前处理条件, 并用柱温程序优化了GC-μECD分析条件. 方法的检出限为0.027～0.087 ng/g; 相对标准偏差为3.4%～7.6% (n=6); 加标平均回收率79.8%～91.1%. 可用于土壤环境中多氯联苯的监测分析.     

Pressurized liquid extraction in determination of polychlorinated biphenyls and organochlorine pesticides in fish samples

Pressurized liquid extraction (PLE) is a relatively new technique applicable for the extraction of persistent organic pollutants from various matrices. The main advantages of this method are short time and low consumption of extraction solvent. The effects of various operational parameters (i.e. temperature of extraction, number of static cycles and extraction solvent mixtures) on the PLE efficiency were investigated in this study. Fish muscle tissue containing 3.2% (w/w) lipids and native polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and other related compounds was used for testing. Purification of crude extracts was carried out by gel permeation chromatography employing Bio-Beads S-X3. Identification and quantitation of target indicator PCBs and OCPs was performed by high-resolution gas chromatography (HRGC) with two parallel electron-capture detectors (ECDs). Results obtained by the optimized PLE procedure were compared with conventional Soxhlet extraction (the same extraction solvent mixtures hexane–dichloromethane (1:1 v/v) and hexane–acetone (4:1 v/v) were used). The recoveries obtained by PLE operated at 90–120 °C were either comparable to “classic” Soxhlet extraction (for higher-chlorinated PCB congeners and DDT group) or even better (for lower chlorinated analytes). The highest recoveries were obtained for three static 5 min extraction cycles.     

A simple and fast micromethod for the analysis of polychlorinated biphenyls in air by sorbent enrichment and ultrasound-assisted solvent extraction

A combination of sorbent enrichment and ultrasound-assisted solvent extraction has been used to determine polychlorinated biphenyls in air. Analytes were sampled by pumping a known volume of air through a porous polymer (Tenax TA). The enriched adsorbent was transferred into a glass vial, and ultrasound-assisted extraction of the analytes was then performed in n-hexane. Quantification was carried out by using gas chromatography coupled to tandem mass spectrometry. Breakthrough volume of the sampling step was studied, indicating that 10 m³ of air could be processed without losses of the most volatile compounds. Good recoveries (75–96%) were obtained, and limits of detection at the sub ng m^–3 were achieved for all the analytes. The proposed method is very simple and fast, avoiding the use of large solvent volumes and time-consuming preconcentration steps.     

Evaluation of Soxhlet extraction, accelerated solvent extraction and microwave-assisted extraction for the determination of polychlorinated biphenyls and polybrominated diphenyl ethers in soil and fish samples

Three commonly applied extraction techniques for persistent organic chemicals, Soxhlet extraction (SE), accelerated solvent extraction (ASE) and microwave-assisted extraction (MAE), were applied on soil and fish samples in order to evaluate their performances. For both PCBs and PBDEs, the two more recent developed techniques (ASE and MAE) were in general capable of producing comparable extraction results as the classical SE, and even higher extraction recoveries were obtained for some PCB congeners with large octanol-water partitioning coefficients (K_ow). This relatively uniform extraction results from ASE and MAE indicated that elevated temperature and pressure are favorable to the efficient extraction of PCBs from the solid matrices. For PBDEs, difference between the results from MAE and ASE (or SE) suggests that the MAE extraction condition needs to be carefully optimized according to the characteristics of the matrix and analyte to avoid degradation of higher brominated BDE congeners and improve the extraction yields.     

Optimized determination of polybrominated diphenyl ethers and polychlorinated biphenyls in sheep serum by solid-phase extraction-gas chromatography-mass spectrometry

We describe a solid-phase extraction (SPE) method, followed by gas chromatography-mass spectrometry (GC-MS), for the simultaneous determination of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in sheep serum samples. The denaturation of serum proteins by formic acid, water-1-propanol and water-2-propanol were compared and optimized. Seven different solid-phase sorbents were tested and it was found that Strata-X cartridge (200 mg, 6 mL) gave the best recoveries (92-106%, SD < 6%, n = 3) for all the target analytes. The different extraction solvents (iso-hexane and dichloromethane), either alone or in combination, were used to extract these persistent organic compounds from spiked serum samples by SPE. Removal of co-extracted biogenic materials was achieved using adsorption chromatography with acid modified silica and activated silica. Iso-hexane was found to be the most appropriate solvent for clean-up providing good recoveries and clear chromatographic separation; its use is preferable to that of DCM because it is less environmentally toxic. The limits of detection (LOD) of the proposed method were 47-105 pg g⁻¹ and 16-24 pg g⁻¹ for the different PBDEs and PCBs studied, respectively. The developed method was linear over the range from 0.05 to 30 ng g⁻¹, for all PBDEs except PBDE 183 (0.10-30 ng g⁻¹), and from 0.02 to 30 ng g⁻¹ for all tested PCB congeners. The established method was successfully applied to sheep serum samples from Scotland, UK, for the determination of the target PBDEs and PCBs.     

Simultaneous extraction and clean-up of polybrominated diphenyl ethers and polychlorinated biphenyls from sheep liver tissue by selective pressurized liquid extraction and analysis by gas chromatography-mass spectrometry

We describe a selective pressurized liquid extraction (SPLE) method, followed by gas chromatography–mass spectrometry (GC–MS), for the simultaneous extraction and clean-up of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in sheep liver tissue samples. The on-line clean-up of liver tissue by SPLE was tested using differing amount of acid-modified silica (sulphuric acid:silica gel, 1:2, w/w), the most effective amount being 20 g. Different extraction solvents (iso-hexane and dichloromethane), either alone or in various combinations, were used to extract these target compounds from spiked liver samples. Variables affecting the SPLE extraction efficiency, including temperature, pressure, number of extraction cycles and static extraction time were studied; the optimum parameters were 80 °C, 10.3 MPa, 2 cycles and 5 min, respectively. The SPLE based method was compared with more traditional Soxhlet, off-line PLE, ultrasonic and heating extraction methods. Overall the mean percentage recoveries for all target chemicals using SPLE were 86–103% (n = 3, SD < 9%), and compared favourably with the Soxhlet (63–109%, n = 3, SD < 8%), off-line PLE (82–104%, n = 3, SD < 18%), ultrasonic (86–99%, n = 3, SD < 11%) and heating (72–102%, n = 3, SD < 21%) extraction methods. The limits of detection of the proposed method were 5–96 pg g⁻¹ and 2–29 pg g⁻¹ for the different PBDE and PCB chemicals studied, respectively. The outputs of the proposed method were linear over the range from 0.02 to 30 ng g⁻¹, for all PCB and PBDE congeners except for PBDE 100 and 153 (0.05–30 ng g⁻¹) and PBDE 183 (0.1–30 ng g⁻¹). The method was successfully applied to sheep liver samples for the determination of the target PBDE and PCB compounds.     

Multiresidue-matrix solid-phase dispersion method for determining 16 organochlorine pesticides and polychlorinated biphenyls in fish

Summary An effective, multiresidue-matrix, solid-phase dispersion — extraction (MSPD) and GC-MS method for the determination of 16 organochlorine pesticides (OCPs), as well as polychlorinated biphenyls (PCBs) from the level chlorination in fish is described. The method uses an octadecylsilyl-derivatized silica and Florisil-based MSPD co-column for direct, on-line clean-up. Recoveries calculated from five different fortification levels are >85% in all cases for OCPs, except for heptachlor and 4,4-DDT where recoveries of 78% and 81% are ob-tained, and >95% for PCBs. Detection limits determined for the OCPs vary from 19.6–91.1 ng g^–1, and from 71.4–111.2 ng g^–1 for the two to five chlorine-containing PCBs. The method has been applied to the analysis of fish grown in Er-Jen river (Taiwan) and method may serve as a screening protocol for the determination of OCPs and PCBs in fish.     

Ultrasound‐assisted extraction and solid‐phase extraction as a cleanup procedure for organochlorinated pesticides and polychlorinated biphenyls determination in aquatic samples by gas chromatography with electron capture detection

The feasibility of developing a quick, easy, efficient procedure for the simultaneous determination of organochlorinated pesticides and polychlorinated biphenyls in aquatic samples using gas chromatography with electron capture detection based on solid‐phase extraction was investigated. The extraction solvent (n‐hexane/acetone, cyclohexane/ethyl acetate, n‐hexane/dichloromethane, n‐hexane) for ultrasound‐assisted solid–liquid extraction and solid‐phase extraction columns (florisil, neutral alumina, acidic alumina, aminopropyl trimethoxy silane, propyl ethylenediamine, aminopropyl trimethoxy silane/propyl ethylenediamine, graphitized carbon black and silica) for cleanup procedure were optimized. The gas chromatography with electron capture detection method was validated in terms of linearity, sensitivity, reproducibility, and recovery. Mean recoveries ranged from 75 to 115% with relative standard deviations <13%. Quantification limits were 0.20–0.40 ng/g for organochlorinated pesticides and polychlorinated biphenyls. The satisfactory data demonstrated the good reproducibility of the method with relative standard deviations lower than 13%. In comparison to other related methods, this method requires less time and solvent and allows for rapid isolation of the target analytes with high selectivity. This method therefore allows for the screening of numerous samples and can also be used for routine analyses.     

微波萃取/气相色谱-质谱测定土壤中的多氯联苯

分别对多氯联苯的微波萃取条件进行了优化。优化后的分析条件为微波功率1200 W,萃取温度115℃,萃取时间20 min,萃取溶剂为V(正己烷)∶V(丙酮)=1∶1。方法的检出限为20~30 ng/g,线性范围40~4000 ng/mL(多氯联苯总量),相关系数均大于0.9990,样品基体加标回收率为92.2%~115%,相对标准偏差为9.4%(n=6)。     

Optimization of solid-phase extraction procedure for determination of polychlorinated dibenzo-<Emphasis Type="Italic">p</Emphasis>-dioxins,polychlorinated dibenzofurans,and coplanar polychlorinated biphenyls in humic acid containing water

A solid-phase extraction (SPE) method was optimized for accurate determination of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (CoPCBs) in humic acid containing surface water. Recovery experiments using humic materials revealed that humic acids permit dioxins to pass through an octadecylsilica (C₁₈) extraction disk by associating with them under weakly alkaline conditions. Acidification of the sample before percolation improved this otherwise insufficient recovery. The analysis of surface water acidified to pH 2 gave better recovery with surrogate standards and lower quantitative values for higher-chlorinated homologues than the sample at pH 9. In all samples, the native octachlorodibenzo-p-dioxin (OCDD) peak abundance showed no difference between at pH 2 and at pH 9, indicating overestimation of the quantitative value of the homologue at pH 9. Acidification of a humic acid containing water sample can avoid overestimation of higher-chlorinated congeners caused by insufficient recovery of their corresponding surrogates.     

Biomass-derived porous material synthesized by one-step calcination method for the magnetic solid-phase extraction of polychlorinated biphenyls in water

Recent findings unfold that biomass materials with the micro/mesoporous structure were often treated as adsorbents for organic substances. In this work, a one-step calcination method was adopted in the preparation of magnetic porous green bean biomass material. It has the properties of magnetism and porosity after the addition of Co(NO₃)₂ and high-temperature calcination. A variety of characterizations have been operated, including energy dispersive X-ray detector, vibrating sample magnetometer, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, and so on. It has a specific surface area of 168.1611 m²/g and a pore volume of 0.1764 cm³/g. The material was used in magnetic solid-phase extraction of three polychlorinated biphenyls: 2-chlorobiphenyl, 4-chlorobiphenyl, and 2,2,5-trichlorobiphenyl. Several factors were investigated, such as material amount, eluents, adsorption time, solution pH, salinity, and reusability. Under optimized conditions, good recoveries (90.24–93.34%) were achieved with the relative standard deviation in a range from 2.30 to 4.83%. Three real water samples (tap, river, and lake water) were tested to verify the accuracy of the method. This method can be successfully used in the analysis of some polychlorinated biphenyls congeners in water.     

Determination of selected polychlorinated biphenyls in water samples by ultrasound-assisted emulsification-microextraction and gas chromatography-mass-selective detection

Ultrasound-assisted emulsification-microextraction (USAEME) procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in 10 mL of water samples by gas chromatography-mass-selective detection. After determination of the most suitable solvent and extraction time, several other parameters including solvent volume, centrifugation time and ionic strength of the sample were optimized using a 2³ factorial experimental design. The optimized USAEME procedure used 200 μL of chloroform as extraction solvent, 10 min of extraction with no ionic strength adjustment at 25 °C and 5 min of centrifugation at 4000 rpm. The limits of detection ranged from 14 ng L⁻¹ (for PCB153) to 30 ng L⁻¹ (for PCB101). Recoveries of PCBs from fortified distilled water are over 80% for three different fortification levels between 0.1 and 5 μg L⁻¹ and relative standard deviations of the recoveries are below 10%. The performance of the proposed method was compared with those involving traditional liquid-liquid extraction (LLE) and solid phase extraction (SPE) on the real water samples (i.e., tap and well water as well as domestic and industrial wastewaters, etc.) and comparable efficiencies were obtained. The proposed USAEME procedure has been demonstrated to be viable, simple, rapid and easy to use for residue analysis of PCBs in water samples.     

Synthesis of stationary phases that provide group recognition for polychlorinated biphenyls by porogenic fragment template imprinting

Molecular recognition based on imprinted polymers results from the polymerization of functional monomers and cross‐linkers in the presence of a target analyte (i.e. template), with subsequent removal of the template to create synthetic binding sites. However, complete removal of the template is difficult to achieve, thereby leading to template leaching, which adversely affects real‐world analytical applications. To overcome this challenge, the present study utilizes porogenic fragment template imprinting techniques to provide an alternative synthetic strategy to generate molecularly imprinted polymers with molecular recognition toward polychlorinated biphenyls. Thereafter, thus‐generated imprinted polymers have been applied as stationary phases in molecularly imprinted solid‐phase extraction for preconcentrating six “indicator polychlorinated biphenyls” in both organic and aqueous media. Recoveries of up to 98.9% (imprinted polymers) versus 73.0% (conventional C₁₈) in an organic phase, and up to 97.4% (imprinted polymers) versus 89.4% (C₁₈) in an aqueous phase have been achieved corroborating the utility of this advanced sorbent material. Finally, porogenic fragment template imprinting strategies have yielded molecularly imprinted polymers that are useful for the quantitative determination of polychlorinated biphenyls in environmental matrices, which provides a low‐cost strategy for tailoring stationary phases that avoid template leaching in applications in solid‐phase extraction as well as liquid chromatography.     

Determination of selected polychlorinated biphenyls in soil by miniaturised ultrasonic solvent extraction and gas chromatography-mass-selective detection

Miniaturised ultrasonic solvent extraction procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in soil samples by gas chromatography-mass-selective detection by using 2³ factorial experimental design. Recoveries of PCBs from fortified soil samples are over 90% for three different fortification levels between 40 and 120 μg kg⁻¹, and relative standard deviations of the recoveries are below 7%. The limits of detection (LODs) ranged from 0.003 to 0.006 μg kg⁻¹. The performance of the proposed method was compared to traditional shake flask extraction method on the spiked real soil sample and extraction methods showed comparable efficiencies. Proposed miniaturised ultrasonic solvent extraction offers several advantages, i.e., reducing sample requirement for measurement of target compound, less solvent consumption and reducing the costs associated with solvent purchase and waste disposal.     

Fast and efficient extraction methods for the analysis of polychlorinated biphenyls and polybrominated diphenyl ethers in biological matrices

This paper describes fast and simple extraction methods for the determination of polychlorinated biphenyls and polybrominated diphenyl ethers in biological matrices. Four extraction protocols were tested. The first protocol used microwave-assisted extraction combined with two purification steps. The second one was similar, except that microwave-assisted extraction was replaced by accelerated solvent extraction. The third one combined extraction/purification by accelerated solvent extraction with final purification on a silica gel column. The last one combined microwave-assisted extraction with purification on an acidic silica gel column. The protocols were tested on various matrices: a spiked matrix, two certified matrices (SRM 2977, WMF 01), and natural matrices (mysids and fish). All of the protocols produced good performance in terms of recovery and reproducibility. The two last protocols showed promising results in terms of applicability to natural matrices, as they required a minimum of sample handling and minimal amounts of solvent and time. These methods allowed at least 24 samples to be handled per day, and could easily be used for routine analysis. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Dispersive liquid-liquid microextraction based on the solidification of floating organic droplet for the determination of polychlorinated biphenyls in aqueous samples

In the proposed method, an extraction solvent with a lower toxicity and density than the solvents typically used in dispersive liquid-liquid microextraction was used to extract seven polychlorinated biphenyls (PCBs) from aqueous samples. Due to the density and melting point of the extraction solvent, the extract which forms a layer on top of aqueous sample can be collected by solidifying it at low temperatures, which form a layer on top of the aqueous sample. Furthermore, the solidified phase can be easily removed from the aqueous phase. Based on preliminary studies, 1-undecanol was selected as the extraction solvent, and a series of parameters that affect the extraction efficiency were systematically investigated. Under the optimized conditions, enrichment factors for PCBs ranged between 494 and 606. Based on a signal-to-noise ratio of 3, the limit of detection for the method ranged between 3.3 and 5.4 ng L⁻¹. Good linearity, reproducibility and recovery were also obtained.     

Fast determination of hydroxylated polychlorinated biphenyls in human plasma by online solid phase extraction coupled to liquid chromatography-tandem mass spectrometry

Hydroxylated polychlorinated biphenyls (OH-PCBs) have been shown to be strongly retained in human blood causing endocrine-related toxicity, particularly on the thyroid system. Traditionally, analytical methods for the determination of OH-PCBs require labor-intensive and long-time consuming sample preparation with several extraction, evaporation and cleanup procedures steps and, in some cases, derivatization prior to the analysis by gas or liquid chromatography-mass spectrometry (GC–MS or LC-MS). The present study developed and validated a novel, sensitive and high throughput online solid phase extraction (SPE) method coupled to LC-tandem mass spectrometry (MS/MS) for the separation and quantitation of relevant congeners of OH-PCBs in human plasma. The developed method presented limits of quantification (LOQ) ranging from 0.02 to 0.5 ng mL⁻¹ and extraction recoveries from 71 to 134% for all congeners, requiring small amount of sample (only 100 μL) and minimal sample preparation. In order to evaluate the applicability of the method, preliminary tests (N = 93) were conducted in plasma from individuals occupationally exposed to very high levels of PCBs in a German cohort. Penta-through hepta-chlorinated OH-PCBs were the predominant congeners in human plasma with concentrations up to 44.5 ng mL⁻¹, while lower chlorinated OH-PCBs were occasionally detected. In addition, a new PCB 28 metabolite has been synthesized and identified for the first time in human plasma and associations between OH-PCBs and their parent compounds in the studied cohort were also assessed.     

Diol sep-pak cartridges for enrichment of polychlorobiphenyls and chlorinated pesticides from water samples; determination by GC-ECD

Summary Gas chromatography of polychlorinated biphenyls and chlorinated pesticides in water samples has been performed after adsorption from a 20–200-mL sample on to a cartridge containing 100 mg diol-bonded porous silica. The PCBs are desorbed with 500 μL ethyl acetate, which is concentrated and analysed by gas chromatography with electron-capture detection (GC-ECD). The average recovery of 0.1 ng mL⁻¹ PCB congeners from distilled water and from Aniene river water is≥95% (standard deviation≤2.8). Average recoveries of 25 ng mL⁻¹ Aroclor 1254 from distilled water and from Aniene river water were, respectively, 94.4% and 92.5% (standard deviation 5.8). In the separation of PCB congeners from the chlorinated pesticides only the aldrin (40%) was eluted with the PCBs from the diol Sep-Pak cartridge by aqueous methanol. The method described is simple and reproducible.