Determination of hexabromocyclododecane isomers in sewage sludge by LC-MS/MS.

A method has been developed to determine alpha, beta and gamma diastereoisomers of hexabromocyclododecane (HBCD), a brominated flame retardant, in sewage sludge, based on the ultrasonic-assisted extraction (UAE) of samples with dichloromethane-ACN (1:1) and the subsequent clean-up of extracts by dispersive solid phase extraction with primary-secondary amine. Levels of HBCD diastereoisomers were determined by LC coupled with ESI MS/MS. Evaluation of the matrix effect showed a high ion suppression for all the diastereoisomers studied, which was counteracted by using a mixture of labelled HBCD diastereoisomers as internal standards. This method yielded recoveries in the range of 79.6-112.5% with SDs equal or lower than 9.1 The limits of detection were 0.3 ng/g for alpha- and beta-HBCD and 0.2 ng/g for gamma-HBCD. The developed method was successfully applied to 19 sludge samples collected from the province of Madrid (Spain). In most of the samples, beta-HBCD was below the method detection limit, whereas alpha- and gamma-HBCD were quantified in all of the sludge samples, and gamma-HBCD was the predominant diastereoisomer in 63% of the analyzed samples and alpha-HBCD predominated in the rest.