Complexation and oxidation strategies for improved TXRF determination of mercury in vaccines
A thorough investigation of strategies to overcome the effect of mercury losses during TXRF analysis was carried out. The vaporisation of mercury on sampling targets, associated with too low concentrations determined, depends on the nature of the respective Hg species and the dwell time of the analytes on the target. To prevent vaporisation, oxidation with ammonium persulfate and complexation with ethylenediamine tetraacetate (EDTA) and dimercaptosuccinic acid (DMSA) were investigated. Whereas both approaches were effective in reducing the Hg losses by vaporisation, the complexation approaches turned out to be particularly efficient. Both EDTA and DMSA retain the different mercury species quantitatively over several hours. Based on this approach, a method for mercury determination by TXRF in liquid samples was developed, successfully validated by inductively coupled plasma optical emission spectrometry and applied to the analysis of a mercury-containing vaccine sample.