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In order to reveal the time-depending mercury species uptake by human astrocytes, a novel approach for total mercury analysis is presented, which uses an accelerated sample introduction system combined on-line with an inductively coupled plasma mass spectrometer equipped with a collision/reaction cell. Human astrocyte samples were incubated with inorganic mercury (HgCl2), methylmercury chloride (MeHgCl), and thimerosal. After 1-h incubation with Hg(2+), cellular concentrations of 3 μM were obtained, whereas for organic species, concentrations of 14-18 μM could be found. After 24 h, a cellular accumulation factor of 0.3 was observed for the cells incubated with Hg(2+), whereas the organic species both showed values of about 5. Due to the obtained steady-state signals, reliable results with relative standard deviations of well below 5 % and limits of detection in the concentration range of 1 ng L(-1) were obtained using external calibration and species-unspecific isotope dilution analysis approaches. The results were further validated using atomic fluorescence spectrometry.

The interaction of Mercurochrome, a medical preparation based on the mercury organic compound merbromin, with free thiols in low molecular weight peptides and in proteins has been investigated by means of liquid chromatography (LC) and electrospray mass spectrometry (ESI-MS). Beta-lactoglobulin A (beta-LGA) from bovine milk (18.4 kDa) has been used as the model protein. It was found that, in contrast to assumptions in literature, the commercial product itself is a heterogeneous mixture of moderate chemical stability, which may contain precipitated Hg salts depending on storage time and conditions. Further variability results from different degrees of bromination of the fluorescein backbone of the compound. The formation of mercury compound-protein adducts was detected. The peptide sequence T13 containing a free thiol residue was identified as the binding site for mercury species after tryptic digestion of beta-lactoglobulin A. While fresh Mercurochrome tends to the formation of a Hg(II)-beta-LGA adducts due to excess Hg(2+) in solution, investigations after precipitation of Hg salts yield Hg(merbromin)(beta-LGA) as the major product.