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.     

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.     

Polychlorinated biphenyls,dibenzo-p-dioxins and dibenzofurans in soil samples from airport areas of Croatia

Levels and patterns of polychlorinated biphenyls (PCBs) were studied in surface soil samples collected in the coastal part of Croatia within and surrounding four different airports and in the vicinity of two partially devastated electrical transformer stations. The compounds accumulated from air-dried soil samples by multiple ultrasonic extraction with an n-hexane?:?acetone 1?:?1 mixture were analysed by capillary gas chromatography with electron capture and ion-trap detection. PCBs were quantified against a standard Aroclor 1242/Aroclor 1260 mixture and a standard mixture of 17 individual PCB congeners (IUPAC No.: 28, 52, 60, 74, 101, 105, 114, 118, 123, 138, 153, 156, 157, 167, 170, 180, and 189). The mass fractions of total PCBs in 18 soil samples collected within the airport premises ranged from 3 to 41?327?µg/kg dry weight (dw) (median: 533?µg/kg?dw), and those in 21 samples collected at a distance ranging from several metres to 5?km away from the airport fence, from <1 to 39?µg/kg?dw (median: 5?µg/kg?dw). The highest PCB levels were determined in soils along the airport aprons where the aircrafts were serviced and refuelled. The PCB pattern was very similar to technical Aroclor 1260 in all airport soils. The PCB pattern in 22 soils collected in the vicinity of electrical transformer stations was dominated by congeners contained in Aroclor 1242. These soils contained 7 to >400?µg/kg?dw of total PCBs. One highly PCB-contaminated airport soil sample was analysed for polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). With an international toxic equivalent (I-TEQ) of 9.7?ng/kg?dw, the airport soil contamination was within values typical for urban and rural areas, and the congener patterns gave no clear indication for PCBs as the only source of PCDDs/PCDFs.     

Determination of polybrominated diphenyl ethers in marine biological tissues using microwave-assisted extraction

Growing concern on the environmental impact of polybrominated diphenyl ethers (PBDEs) has created the need for rapid and quality assured analytical methods to quantify PBDEs in a spectrum of matrix types. This study presents the first validated method for the quantification of major PBDE congeners (47, 99 and 100) in marine biological tissues using microwave-assisted extraction (MAE). The recovery of polychlorinated biphenyls and various organochlorine pesticides has also been ascertained. Analytical accuracy, precision, limits of detection and cleanup efficiency were evaluated for PBDE congeners, and empirical data justifies the use of MAE for the extraction and analysis of PBDEs in biological matrices. MAE was also compared to Soxhlet extraction efficiency for PBDEs in the standard reference materials SRM2978 and SRM1588a and gave comparable results (<15% variation).     

Use of experimental design in the optimisation of stir bar sorptive extraction followed by thermal desorption for the determination of brominated flame retardants in water samples

A method for the determination of polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) in water samples is proposed. The method involving stir bar sorptive extraction (SBSE) and thermal desorption followed by gas chromatography coupled with mass spectrometry was optimised using statistical design of experiments. In the first place, the influence of different polydimethylsiloxane stir bars was studied. A Plackett–Burman design was chosen to estimate the influence of five factors on the efficiency of the SBSE process: desorption time (5–10 min), desorption temperature (250–300 °C), desorption flow (50–100 mL min⁻¹), cryofocusing temperature (-130 to 40 °C) and vent pressure (0–12.8 psi). Afterwards, two central composite designs were used to find the optimal process settings that were applied to the optimisation of both desorption and extraction efficiency. In the case of the desorption parameters, long desorption times (10 min) and desorption flows lower than 70 mL min^-1 yielded the best signals for the majority of compounds. However, different behaviour among the analytes was observed for the vent pressure and we decided to fix it at an intermediate value (7 psi). In the case of extraction parameters, the sample volume and the addition of NaCl did not have a significant effect, while the addition of methanol yielded better extraction responses. Remarkable recovery (82–106%) and repeatability (less than 18%) were attained. Furthermore, excellent regression coefficients (r ² = 0.991–0.999) and low detection limits (1.1–6.0 ng L⁻¹) were also achieved for the congeners studied. The proposed method was applied to the analyses of PBDEs and PBBs in waters from the Basque Country, Spain.     

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.     

Potential chlorinated and brominated interferences on the polybrominated diphenyl ether determinations by gas chromatography-mass spectrometry

The analysis of polybrominated diphenyl ether (PBDE) congeners by GC-MS was studied in terms of potential interferences. Different MS approaches were normally used for the PBDE analyses: negative ion chemical ionization (NICI-MS) and electron ionization (EI-MS). This paper studied the presence of potential interferences in each instrumental technique approach, principally those corresponding to different chlorinated compounds (PCBs, PCNs, etc.) as well as brominated compounds (PBBs, MeO-PBDEs, TBBPA, etc.). The two ionization modes are subjected to different types of interferences. In general, EI-MS is affected by chlorinated interferences, especially PCBs. NICI-MS eliminated chlorinated interferences but presented different brominated interferences, well resolved with the EI-MS approach.     

Determination of persistent organohalogenated pollutants in human hair reference material (BCR 397): an interlaboratory study

A human powdered hair material (BCR 397) was tested for its content in persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs). Using different methods, three laboratories (two from Canada and one from Belgium) analysed a powdered hair sample to evaluate some methodologies and to obtain consensus values for selected POPs. Measured values for all PCB congeners and p,p-DDE were within a relative standard deviation (RSD) of 15%. These first results contribute to the accuracy and precision for POPs quantification in hair and render test results more comparable among different laboratories.     

Gas chromatographic retention of 180 polybrominated diphenyl ethers and prediction of relative retention under various operational conditions

The gas chromatographic (GC) retention times of 180 polybrominated diphenyl ethers (PBDEs) were obtained under different operational conditions on two types of commonly used capillary columns, Restek Rtx-1614 and J&W DB-5MS, of different dimensions. The relative retention times (RRTs) for PBDEs were calculated by normalizing the retention times of individual congeners to the sum of those of BDEs 47 and 183. In clear contrast to polychlorinated biphenyls (PCBs), the elution of PBDEs has few cross-homolog overlaps, and this observation is discussed in terms of molecular conformation with regard to co-planarity. Within a homolog, ortho substitution in PBDEs tends to decrease GC retention, and such an effect is stronger for higher homologs. With the RRT database established in this work, a simple approach is evaluated for the identification of all mono to hepta PBDEs from the RRTs of 39 congeners under various GC conditions to facilitate the identification of unknown PBDE peaks for which chemical standards are not available.     

Validation of methods for measuring polychlorinated dibenzo- p -dioxins and furans,and dioxin-like polychlorinated biphenyls in flue gas

Method validation was performed on the collection and extraction procedures for an analysis of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and dioxin-like polychlorinated biphenyls (DLPCBs) in flue gas. The adoption of the rapid pressurized liquid extraction (PLE) technique was evaluated for extraction from polyurethane foam plugs (PUFPs) and fly ash. With respect to extraction from PUFPs, dichloromethane PLE showed an extraction efficiency equivalent to that of conventional acetone Soxhlet, while toluene PLE was found to have a lower extraction efficiency from fly ash than toluene Soxhlet. The collection ability of three sampling methods, employed in the Japanese standard analytical method JIS K0311 (revised in 2005) was evaluated by evaluating the distribution of gaseous PCDD/Fs and DLPCBs in each collection compartment in sampling trains. A DiOANA® fibrous alumina filter and a PUFP, newly employed trapping devices in the revised JIS method, were found to trap gaseous analytes effectively. The validation of the two newly employed sampling methods (DiOANA and PUFP) was tested by parallel measurements of the methods with a conventional five-impinger method, and good agreements on the PCDD/Fs and DLPCBs quantities were demonstrated.     

Gas chromatography-mass spectrometric determination of polybrominated diphenyl ethers in complex fatty matrices from aquaculture activities

Gas chromatography coupled to mass spectrometry in negative chemical ionization mode (GC-(NCI)MS) has been applied to the quantification and reliable identification of polybrominated diphenyl ethers (PBDEs) in animal and vegetable samples from aquaculture activities. Matrices analyzed included fish fillet, fish feed, fish oil and linseed oil, their fat content ranged from 5% to 100%. Solid-phase extraction (SPE) (using Florisil and silica cartridges) and normal-phase high performance liquid chromatography were tested for an efficient clean-up in order to obtain sample extracts free of interfering compounds. Combining sulphuric acid digestion and SPE with Florisil led to the highest efficiency in the elimination of interferences from the extracts. The sample procedure developed, together with the application of GC-(NCI)MS for measurement, led to the satisfactory determination of PBDEs at μg kg ⁻¹ levels in complex aquaculture matrices with high lipid content. The use of a short and thin film-thickness fused-silica capillary column allowed to determine the problematic BDE 209 with satisfactory results. Three m/z ions were acquired for each analyte, which ensured a reliable identification of compounds detected in samples.     

Determination of polybrominated diphenyl ethers in milk samples. Development of green extraction coupled techniques for sample preparation

Ultrasound‐assisted extraction (UAE), cloud point extraction (CPE), and ultrasound back‐extraction (UABE) techniques have been coupled for lixiviation, preconcentration, and cleanup of polybrominated diphenyl ethers (PBDEs) from milk samples for determination by gas chromatography‐electron capture detection (GC‐ECD). Physicochemical parameters that affect the efficiency of the extraction system were investigated using a design of experiments based on multivariate statistical tools, and considering the sample matrix along the development. The coupling of the leaching step, UAE, enhanced ca. 3.5 times the extraction efficiency of the former sample preparation methodology (CPE‐UABE) leading to cleaner sample extracts suitable for GC analysis. Under optimum conditions, the proposed methodology exhibits successful performance in terms of linearity and precision, with recoveries in the range of 68–70% and LODs within the range 0.05–0.5 ng/g dry weight (d.w.). The proposed sample preparation methodology coupled three green analytical techniques. It expands the application frontiers of CPE for the analysis of biological samples by GC. The optimized methodology was used for determination of PBDEs in powder milk samples, from both commercial and human sources.     

New multiresidue analytical method dedicated to trace level measurement of brominated flame retardants in human biological matrices

A new method has been developed for the multi-residue measurement of the main brominated flame retardants (alpha- and gamma-hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBP-A) and polybrominated diphenyl ethers including decabromodiphenyl ether) in human biological matrices (serum, adipose tissue and breast milk). The proposed sample preparation procedure focused on reduced solvent and consumable consumption and associated procedural contamination, as well as reduced sample size. This protocol was fully validated and was proved to be suitable for identification of brominated flame retardant residues at ultra-trace level, as attested by preliminary results on real samples.     

Shpol'skii spectroscopy at the interface of two non-polar microenvironments: a novel approach for the analysis of polycylic aromatic compounds

This article presents a thorough investigation of quantitative parameters for the analysis of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans (PDBFs) partitioning between an octadecyl silica extraction membrane and microliters of an n-alkane solvent spiked on the surface of the membrane. Shpol'skii spectrometry is directly performed on the surface of the membrane with the aid of a cryogenic fiber optic probe. The analyte concentration in the layer of Shpol'skii solvent follows a linear relationship with the analyte concentration in the water sample and the same is observed for the phosphorescence signal of the cryogenic probe. The accuracy and precision needed for quantitative analysis in aqueous samples is demonstrated. The analytical figures of merit show the feasibility to determine organic pollutants at the parts-per-trillion level with minimum solvent consumption.     

Instrumental methods and challenges in quantifying polybrominated diphenyl ethers in environmental extracts: a review

Increased interest in the fate, transport and toxicity of polybrominated diphenyl ethers (PBDEs) over the past few years has led to a variety of studies reporting different methods of analysis for these persistent organic pollutants. Because PBDEs encompass a range of vapor pressures, molecular weights and degrees of bromine substitution, various analytical methods can lead to discrimination of some PBDE congeners. Recent improvements in injection techniques and mass spectrometer ionization methods have led to a variety of options to determine PBDEs in environmental samples. The purpose of this paper is therefore to review the available literature describing the advantages and disadvantages in choosing an injection technique, gas chromatography column and detector. Additional discussion is given to the challenges in measuring PBDEs, including potential chromatographic interferences and the lack of commercial standards for higher brominated congeners, which provides difficulties in examining degradation and debromination of BDE congeners, particularly for BDE 209.     

Microextraction techniques for the determination of volatile and semivolatile organic compounds from plants: A review

Vegetables and fruits are necessary for human health, and traditional Chinese medicine that uses plant materials can cure diseases. Thus, understanding the composition of plant matrix has gained increased attention in recent years. Since plant matrix is very complex, the extraction, separation and quantitation of these chemicals are challenging.     

Trends in techniques for the extraction of drugs and pesticides from biological specimens prior to chromatographic separation and detection

The isolation of non-volatile organic poisons from biological specimens is often difficult and time consuming. This paper surveys the isolation of common drugs and pesticides from biological specimens, including serum, blood and tissue, and the effect of experimental variables on the recovery of compounds, with emphasis on recent trends in extraction techniques and new methods under development, particularly those applicable to forensic toxicology. Traditional liquid-liquid extraction techniques are increasingly being replaced by or used in combination with newer extraction techniques such as solid-phase and supercritical fluid extraction. The potential advantages and problems encountered when incorporating these new methodologies in the isolation of drugs and pesticides from biological matrices are discussed. Although early implementation of solid-phase extraction techniques in forensic toxicology has been hampered by a variety of problems, including extract quality, reproducibility and selectivity, improvements in sorbent quality and elution solvents continue to facilitate their replacement of traditional liquid-liquid extraction methods. Future developments in supercritical fluid extraction should allow this technique to develop in an extremely powerful quantitative tool for the isolation of drugs and pesticides either from solid-phase sorbents or from their endogenous matrices.     

Concurrent extraction,clean‐up,and analysis of polybrominated diphenyl ethers,hexabromocyclododecane isomers,and tetrabromobisphenol A in human milk and serum

A method has been developed and validated for the concurrent extraction, clean‐up, and analysis of polybrominated diphenyl ethers (PBDEs), α‐, β‐, and γ‐hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA) in human milk and serum. Milk and serum samples were extracted using accelerated solvent extraction with acetone/hexane 1:1, v/v and liquid–liquid extraction with methyl‐tert‐butyl ether/hexane 1:1, v/v, respectively. The removal of co‐extracted biogenic materials was achieved by gel permeation chromatography followed by sulfuric acid treatment. The fractionation of the PBDEs and HBCD/TBBPA was performed using a Supelco LC‐Si SPE cartridge. The detection of the PBDEs was then performed by GC–MS and that of the HBCDs and the TBBPA was performed using UPLC–MS/MS. The pretreatment procedure was optimized, and the characteristic ions and fragmentation of the analytes were studied by MS or MS/MS. A recovery test was performed using a matrix spiking test at concentrations of 0.05–10 ng/g. The recoveries ranged from 78.6–108.8% with RSDs equal to or lower than 14.04%. The LODs were 1.8–60 pg/g. The usefulness of the developed method was tested by the analysis of real human samples, and several brominated flame retardants in different samples were detected and analyzed.     

Sample preparation for peptides and proteins in biological matrices prior to liquid chromatography and capillary zone electrophoresis

The determination of peptides and proteins in a biological matrix normally includes a sample-preparation step to obtain a sample that can be injected into a separation system in such a way that peptides and proteins of interest can be determined qualitatively and/or quantitatively. This can be a rather challenging, labourious and/or time-consuming process. The extract obtained after sample preparation is further separated using a compatible separation system. Liquid chromatography (LC) is the generally applied technique for this purpose, but capillary zone electrophoresis (CZE) is an alternative, providing fast, versatile and efficient separations. In this review, the recent developments in the combination of sample-preparation procedures with LC and CZE, for the determination of peptides and proteins, will be discussed. Emphasis will be on purification from and determination in complex biological matrices (plasma, cell lysates, etc.) of these compounds and little attention will be paid to the proteomics area. Additional focus will be put on sample-preparation conditions, which can be hard or soft, and on selectivity issues. Selectivity issues will be addressed in combination with the used separation technique and a comparison between LC and CZE will be made.