New perspectives on diastereoselective determination of hexabromocyclododecane traces in fish by ultra high performance liquid chromatography-high resolution orbitrap mass spectrometry

A new analytical method is presented for diastereoisomer-specific identification and quantitation of hexabromocyclododecanes (HBCD) in fish samples. The method is based on extraction of the target analytes from samples with a mixture of organic solvents, with further three-stage clean-up including destructive removal of matrix components with sulphuric acid and acid-impregnated silica gel, and Florisil adsorption column chromatography. Ultra high performance liquid chromatography (UPLC) coupled with high resolution (HR) Orbitrap mass spectrometry featuring heated electrospray ionization (HESI-II) interface operated in negative ion mode was employed for the identification/quantitation of contaminants. The developed methodology was robustly validated in terms of recovery, repeatability, intermediate precision, linear calibration ranges, limits of detection and quantitation, and used for analysis of twenty five Baltic wild salmon (Salmo salar) samples. Under the optimized conditions, recoveries for selected analytes were within the range of 91.4-103.6%, and the repeatability and intermediate precision in terms of relative standard deviations (RSDs) were in the ranges 1.6-8.3% and 1.6-12.5%, respectively, for all three validation levels. The elaborated method achieved instrumental limits of quantification (i-LOQ) of 1.3-3.0pg on column for three HBCD diastereoisomers corresponding to the method LOQ of 0.005-0.012ngg^-1 wet weight (w.w.) The presence of HBCD diastereoisomers was confirmed in all the analyzed Baltic salmon samples in the concentration range of 0.39-3.82ngg^-1 w.w. with an average of 1.59ngg^-1 w.w. for total HBCD. The diastereomer pattern typical for aquatic biota was observed with strong predominance of α-HBCD. The newly developed methodology could be employed for a regular diastereomer-specific monitoring of HBCD content in fish samples, representing a good alternative to existing LC-MS/MS methods in terms of sensitivity and accuracy, and providing further possibilities for inclusion of other contaminants in the scope of analysis.