Analysis of hydroxylated polybrominated diphenyl ether metabolites by liquid chromatography/atmospheric pressure chemical ionization tandem mass spectrometry

Hydroxylated polybrominated diphenyl ether (OH‐PBDEs) metabolites have the potential to cause endocrine disruption as well as other health effects. Currently, gas chromatography/mass spectrometry (GC/MS) after derivatization is used for the analysis of OH‐PBDEs. However, there is a need for the direct analysis of OH‐PBDEs at relatively low concentrations in environmental and biological samples. Liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry (LC/APCI‐MS/MS) was evaluated for the analysis of nine OH‐PBDEs, ranging from tri‐ to hexabrominated. Separation of the nine isomeric metabolites was achieved with reversed‐phase liquid chromatography, followed by detection by APCI‐MS in negative mode. Notably, a significant decrease in ionization was observed in 6‐hydroxyl‐substituted PBDE metabolites in the presence of an ortho‐substituted bromine, relative to the other hydroxylated metabolites. This is probably due to the formation of dioxins in the source as a result of the high‐temperature conditions, which prevented ionization by hydrogen abstraction. The MS/MS experiments also provided evidence of the neutral losses of HBr and Br₂, indicating the possible use of neutral loss scanning and selected reaction monitoring (SRM) for the screening of brominated metabolites in samples. The applicability of LC/APCI‐MS/MS was demonstrated for the analysis of metabolites of BDEs 47 and 99 formed in human liver microsomes. The LC/APCI‐MS/MS method was able to detect metabolites that had previously been identified by GC/MS following derivatization. Copyright © 2010 John Wiley & Sons, Ltd.