Improving the sensitivity of liquid chromatography–tandem mass spectrometry analysis of hexabromocyclododecanes by chlorine adduct generation

It is well documented and experimentally confirmed that hexabromocyclododecanes (HBCDs) tend to associate with several anions forming different adducts that can affect the sensitivity and the accuracy of the determinations. In the present work, two different approaches for HBCD determination have been optimised and characterised based on their repeatability and intermediate precision, linear calibration ranges, sensitivity, limits of detection and quantification and application to commercial food samples. Both methods involve the use of a triple quadrupole mass spectrometer coupled to a liquid chromatograph and the addition of different ammonium salts to the mobile phase, i.e. ammonium chloride or ammonium acetate, in order to encourage (Cl method) or try to inhibit (Ac method), respectively, the formation of the chlorine adducts of the molecular ion. Precision of the two methods investigated was similar and both approaches presented a comparable behaviour for the analysis of food samples. However, the Cl method showed higher sensitivity and the limits of detection (0.23–0.41 pg on column) and quantification (0.77–1.35 pg on column) were up to 14 times lower than those obtained applying the Ac method. All these facts make the Cl method the best choice for the quantification of HBCDs in food samples with low concentration levels.