Determination of ten hexabromocyclododecane diastereoisomers using two coupled reversed-phase columns and liquid chromatography/tandem mass spectrometry.

Abstract

Hexabromocyclododecanes (HBCDs) are raising concern due to their potential persistence, bioaccumulation and toxicity. Apart from the widely reported isomers α-, β-, γ-HBCD, other HBCD diastereoisomers such as δ-HBCD have been also recently found in environmental media and biota. These newly reported diastereoisomers might give more insight into the degradation and biotransformation of HBCDs. A reversed-phase C18 column coupled to a C8 column was used to improve the chromatographic resolution. A gradient mobile phase consisting of methanol, acetonitrile, and water, as well as tandem mass spectrometry parameters, were optimized. Ten HBCD diastereoisomers were finally determined by liquid chromatography/tandem mass spectrometry in multiple reaction monitoring mode with negative electrospray ionization. Eight of the ten HBCDs could be chromatographically separated by using the coupled reversed-phase columns. Results of the method validation indicate high reproducibility and good sensitivity. The limit of detection ranged from 0.4 to 0.8 pg, and the relative standard deviations of intra- and inter-day injections ranged from 1.8 to 5.1% and from 2.7 to 9.5%, respectively. The developed method was further applied to the analysis of HBCDs in HBCD commercial products and soil samples. δ-, η-, θ-, and ε-HBCD were detected in commercial products and soil samples. The present study revealed that δ-, η-, θ-, and ε-HBCD might occur ubiquitously in environmental media and biota. These newly reported diastereoisomers may help us to better understand the fate and transformation of HBCDs in the environment.