Dialysis with a semipermeable membrane – a new sample-preparation technique for determination of Polybrominated Diphenyl ethers in fatty matrices

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Summary

Dialysis with a low-density polyethylene semipermeable membrane (SPM) is an efficient means of removal of lipids in the determination of bioaccumulative, persistent, halogenated organic compounds. In this study an SPM was used for preconcentration of polybrominated diphenyl ethers (PBDE) from food samples. The method is useful for determination of PBDE and other halogenated persistent organic pollutants in fatty food samples. In this work chocolate, butter, chicken eggs, pork, and salmon fat were analyzed. Lipid carry-over values (%LC) are reported and recovery of the analytes for the whole procedure was determined by fortifying fish fat with six natural PBDE internal standards which were normally present in the sample at levels below the limit of detection.

Introduction

Flame-retardant chemicals are added to plastics, textiles, electronic circuitry, and other materials to slow the burning process and prevent fires. Some technical flame-retardant products contain brominated organic com-pounds. The most widely used brominated flame-retardants (BFR) are po-lybrominated diphenyl ethers (PBDE), hexabromocyclododecane (HBCD), tetrabromobisphenol-A (TBBP-A), and polybrominated biphenyls (PBB) [1]. Commercial PBDE products consist predominantly of penta, octa, and decabromodiphenyl ether products. Decabromodiphenyl ether is the most widely used PBDE product. Polybrominated diphenyl ethers (PBDE) are added to a wide range of materials at concentrations up to 30% by weight [2]. They are commonly added to high-impact polystyrene, flexible poly-urethane foam, textile coatings, cable insulation, and electrical and electronic equipment [3]. Polybrominated diphenyl ethers are unreactive and so are not incorporated into the polymeric materials by bonding between the polymer and the flame retardant. They may, therefore, leach from pro-ducts into the environment [4]. PBDE were first discovered in pike, eel, and sea trout from Sweden in 1981. Since then, researchers in Europe, Ca-nada, and the USA have confirmed the presence of PBDE in a variety of environmental samples, primarily detecting the lower brominated isomers, for example tetra and penta-BDE [5]. Polybrominated diphenyl ethers are persistent, lipophilic, and bioaccumulating chemicals. They are toxic to humans and animals [6].

Sample preparation is important in the analysis of PBDE in food samples, because such samples require highly efficient methods of purify-cation before final analysis. Dialysis, with a semipermeable membrane (SPM), of solution of an extract in an organic solvent enables separation of organohalogen contaminants, for example PBDE, from lipids. The ob-jective of this study was application of SPM clean-up to the determination of PBDE in animal or plant fat. SPM enable nondestructive separation of the analyte from matrix compounds, which can be useful for preconcen-tration of organic chemicals in animal or plant fat samples. The membra-nes are made from low-density polyethylene film with approximately 1-nm pores; these enable permeation of small (analyte) molecules whereas di-alysis of molecules of matrix compounds larger than this is not possible [7–9]. The membrane is shaped into a narrow tube which is sealed at one end. The thickness of the polyethylene film used in this work was appro-ximately 80 μm [10]. The method can be used for efficient and inexpensive clean-up of animal fat samples. SPM sample clean-up can be used for determination of other persistent organic pollutants in the environment, for example pesticides [11], polychlorinated biphenyls (PCBs) [12], and polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) [13].

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