Semiautomated high-throughput extraction and cleanup method for the measurement of polybrominated diphenyl ethers and polybrominated and polychlorinated biphenyls in breast milk

A semiautomated extraction and cleanup method has been developed to measure eight polybrominated diphenyl ethers (PBDEs), 2,2′,4,4′5,5′- hexabromobiphenyl (BB-153), and 2,2′,4,4′,5,5′- hexachlorobiphenyl (CB-153). The method employs solid-phase dispersion on diatomaceous earth in a solid-phase extraction cartridge followed by automated addition of internal standards (¹³C-labeled). Extraction is then performed using an automated modular solid-phase extraction system. The extraction procedure includes drying the sample on diatomaceous earth by pressurized nitrogen and eluting target analytes and lipids with dichloromethane. Lipid content is determined gravimetrically. Lipid determinations performed using this method are compared with other standard methods and with a certified reference material. A relative standard deviation of 7.9% was obtained for 130 determinations of the lipid content in a breast milk quality control sample. Final analytical determination of target analytes was performed by gas chromatography-isotope dilution high-resolution mass spectrometry. Relative standard deviations for the measurements of target analytes for which a labeled internal standard was available were below 10% for analytes at concentrations above 1 ng/g of lipid. Mean recoveries of the ¹³C-labeled internal standards ranged from 60 to 89% for the eight PBDE congeners; 74 and 113% were recovered for BB-153 and CB-153, respectively.