▎ 摘　　要

Determination of thiomersal was made by the temporally selective photo-degradation, mediated by graphene quantum dots (GQDs) and TiO(2 )nanoparticles (GQDs-TiO2 ) composite, producing the Hg0 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-TiO2 (0.18 mg L-1). Hg-0 temporal profile from thiomersal was detected after 16 min of UV exposure. Different kinetics of Hg0 releasing allowed speciation as the Hg0 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 Hg2+ and then into Hg-0. The method was applied in the determination of thiomersal in vaccines and residual levels of Hg2+ and ethylmercury were also detected.