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 ((13)C-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 (13)C-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.

Semiautomated high-throughput extraction and cleanup method for the measurement of polybrominated diphenyl ethers, polybrominated biphenyls, and polychlorinated biphenyls in human serum.

A semiautomated extraction and cleanup method has been developed for the measurement of 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 automated addition of internal standards ((13)C-labeled), addition of formic acid (denaturation agent), and dilution with water prior to automated overnight extraction using a modular solid-phase extraction (SPE) system. Removal of coextracted biogenic materials was performed on a two-layered 3-mL disposable cartridge containing activated silica gel and a mixture of silica gel and sulfuric acid. Sample cleanup was automated using the same modular SPE system. Reproducibility and precision of the liquid handler used for internal standard additions were shown to be 2 and 4%, respectively. Overall reproducibility during processing of eight batches of samples (N = 30/batch, including methods blanks) was below 10% for most analytes. Mean recoveries of the (13)C-labeled internal standards ranged from 69 to 95% for the seven monitored PBDEs; 76 and 98% were recovered for BB-153 and CB-153, respectively.