Interference of Sb(III) in the Determination of Hexavalent Chromium in Thermoplastic Matrices

摘要

Due to the adverse health effects of hexavalent chromium, Cr(Ⅵ), pigments and other materials containingCr(Ⅵ) were largely banned for use in electrotechnical products under the EU RoHS Directive [1]. Whilethere are several effective methods to determine the presence of total chromium in electrotechnical plasticmatrices, a validated compliance test method that is capable of discerning Cr(Ⅵ) from the non-regulatedforms of Cr(Ⅲ) is not yet available. One of the challenges in developing a standardized compliance testfor Cr(Ⅵ) is the low recovery of Cr(Ⅵ) compounds from polymer matrices This study identifiedantimony trioxide (ATO), a common synergist added to enhance the ignition resistance of brominatedflame retardants (BFRs), as a source of matrix interference in the quantitative determination of hexavalentchromium extracted from polymer matrices. ATO reduces hexavalent chromium to trivalent chromiumprior to complexation of Cr(Ⅵ) with diphenylcarbazide (DPC) leading to false negatives. EDTA wasfound to be an efficient reagent for Sb(Ⅲ) complexation, thereby suppressing the reduction of Cr(Ⅵ) andenabling quantitative Cr(Ⅵ) determination in the presence of ATO.