Identification of polybrominated diphenyl ether metabolites based on calculated boiling points from COSMO-RS, experimental retention times, and mass spectral fragmentation patterns

The COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) was used to predict the boiling points of several polybrominated diphenyl ethers (PBDEs) and methylated derivatives (MeO-BDEs) of monohydroxylated BDE (OH-BDE) metabolites. The linear correlation obtained by plotting theoretical boiling points calculated by COSMO-RS against experimentally determined retention times from gas chromatography-mass spectrometry facilitated the identification of PBDEs and OH-BDEs. This paper demonstrates the applicability of COSMO-RS in identifying unknown PBDE metabolites of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) and 2,2′,4,4′,6-pentabromodiphenyl ether (BDE-100). Metabolites of BDE-47 and BDE-100 were formed through individual incubations of each PBDE with recombinant cytochrome P450 2B6. Using calculated boiling points and characteristic mass spectral fragmentation patterns of the MeO-BDE positional isomers, the identities of the unknown monohydroxylated metabolites were proposed to be 2′-hydroxy-2,3′,4,4′-tetrabromodiphenyl ether (2′-OH-BDE-66) from BDE-47, and 2′-hydroxy-2,3′,4,4′,6-pentabromodiphenyl ether (2′-OH-BDE-119) and 4-hydroxy-2,2′,3,4′,6-pentabromodiphenyl ether (4-OH-BDE-91) from BDE-100. The collective use of boiling points predicted with COSMO-RS, and characteristic mass spectral fragmentation patterns provided a valuable tool toward the identification of isobaric compounds.