Determination of mercury (thimerosal) in vaccines using different oxidants and cold vapor atomic fluorescence spectrometry in dilute acids

Abstract

A simple and fast method was developed for the determination of thimerosal (TH) in vaccines based on decomposition through the action of oxidizing systems of the organic mercury compound to inorganic mercury (Hg_ino) using cold vapor atomic fluorescence spectrometry (CVAFS) for detection. The oxidative decomposition of TH to Hg_ino was evaluated in four oxidizing systems: (1) KBr/KBrO₃; (2) KMnO₄; (3) KI/KIO₃; and (4) Na₂S/KMnO₄ employing diluted mineral acids. Only the systems (1) and (2) presented quantitative oxidation to Hg_ino. The method presented high sensitivity under optimized conditions with a LOD of 0.02 μg L⁻¹ and proved to be accurate with an RSD of ≤4.59%. The absence of a matrix effect was proven from the recovery tests applied to the vaccine samples, fortified with TH, obtaining recoveries of 80.1 to 106% (system 1) and 92.5 to 101% (system 2). Finally, the method was applied to five vaccine samples with differing TH concentrations, and the results were in agreement with a microwave-assisted digestion methodology (reference method), thus indicating the accuracy of the proposed method.