Analysis of Mercurial Preservatives in Different Vaccines by Cold Vapor Atomic Absorption Spectrophotometry

Vaccines with low concentration of mercurial preservatives, such as thiomersal, are in use in Albania. A simple and a sensitive method by using CVAAS method for the determination of mercury in vaccine samples is described. This method is based on a digestion procedure that transforms organic mercury to Hg2+. Digestion is a critical step to destroy microorganism that could combine with Hg2+ and metabolize into ethyl mercury, thus preventing the mercury determination via CVAAS method. Negative chemical interferences were observed, after acid digestion of vaccine samples by obtaining low repeatability of the results. The method was improved by using heating (80℃-90℃), UV radiation and digestion with strong oxidants and acids to transform organic mercury into Hg2+ for CVAAS determination. The accuracy of the analysis was checked by recovery of the spikes which was in the range of 98-102%. The method yielded reproducible results with RSD<5.5%.