Thiomersal determination in vaccines using graphene quantum dots-TiO2 nanocomposite to promote temporally selective photo-production of Hg cold vapor

Determination of thiomersal was made by the temporally selective photo-degradation, mediated by graphene quantum dots (GQDs) and TiO 2 nanoparticles (GQDs-TiO 2 ) composite, producing the Hg 0 quantified by atomic absorption spectrometry (AAS) using a multipass detection cell. The UV photo-reactor was directly adapted to the mercury dedicated spectrometer with samples mixed, into quartz tube, to a solution (buffered at pH 4.0) containing formic acid (1% v /v) and the dispersed GQDs-TiO 2 (0.18 mg L −1 ). Hg 0 temporal profile from thiomersal was detected after 16 min of UV exposure. Different kinetics of Hg 0 releasing allowed speciation as the Hg 0 from other mercurial species were produced at different times. Analytical linear range was from 15 ng L −1 (LOD) up to 1000 ng L −1 . Temporal separation of Hg 0 formation was confirmed by gas chromatography coupled to atomic fluorescence spectrometry, also indicating that thiomersal is firstly degraded to ethylmercury before turning into Hg 2+ and then into Hg 0 . The method was applied in the determination of thiomersal in vaccines and residual levels of Hg 2+ and ethylmercury were also detected. • CV_AAS thiomersal quantification was made after photo-degradation with GQDs-TiO 2 . • Temporal formation of Hg 0 allowed selectivity towards other mercurial species. • Thiomersal was converted into Hg 0 without use of further chemical reduction of Hg 2+ . • Mechanism of thiomersal photo-degradation was studied. • Thiomersal was determined in vaccines along with residual ethylmercury and Hg 2+ .