Simultaneous Determination of α-, β- and γ- hexabromocyclododecane Diastereoisomers in Sewage Sludge using Liquid Chromatography Tandem Mass Spectrometry

Abstract

Hexabromocyclododecane (HBCD) is a large-scale usage brominated flame retardant consisting of a mixture of diastereoisomers which has been reported as an ubiquitous environmental contaminant. HBCD has attracted much attention due to its toxicity and increasing levels in waste water sewage sludge. Since November 2014, HBCD was added to the Persistent Organic Pollutants list of the Stockholm Convention which generated a higher concern regarding its presence in the environment. A rapid (8 min) and accurate liquid chromatography electrospray ionization tandem mass spectrometry method (LC-ESI-MS/MS) was developed to separate and detectα-, β- and γ-HBCD isomers from sewage sludge. Optimization of LC-MS parameters (column temperature, mobile phase composition and flow, collision energy, fragmentor voltage, capillary voltage and drying gas temperature) allowed complete separation of the three isomers and also very good detection sensitivity with instrumental quantitation limits (IQLs) between 0.3 and 0.6 ng/mL. The three isomers were separated on a C18 reversed-phase column, kept at 18°C, using a H2O/ACN/MeOH mobile phase mixture and detected by negative electrospray ionization using MRM mode with two transitions, one for quantitation and one for confirmation. MS detector response was linear in the range 1.0 ÷ 100.0 ng/ mL with correlation coefficients (R2) higher than 0.99 for all three isomers. A simple ultrasonic assisted liquid-solid extraction procedure using a solvent mixture was employed to extract HBCD isomers from WWTP sewage sludge. Overall method intra-day and inter-day precision (RSD%) were situated between 7.6 ÷ 9.2% and 10.3 ÷ 14.5%, respectively. LOQs forα-,β- and γ-HBCD were 1.4, 0.7 and 1.0 ng/g, comparable and even lower to those reported by similar studies concerning HBCD presence in WWTP sewage sludge. HBCD presence was tested from several WWTP sludge samples. All three isomers were found with 100% detection frequency ranging from 3 to 76 ng/g.