Cold vapour atomic fluorescence studies on the behaviour of mercury(II) and mercury(II)-thiol complexes. An alternative route for characterization of-SH binding groups
E. Bramanti et al., Cold vapour atomic fluorescence studies on the behaviour of mercury(II) and mercury(II)-thiol complexes. An alternative route for characterization of-SH binding groups, J ANAL ATOM, 14(2), 1999, pp. 179-185
The behaviour of Hg-II and Hg-II-thiol complexes (RSH = L-cysteine, DL-peni
cillamine, propane-2-thiol, glutathione, thiosalicylic acid) following thei
r reduction with alkaline sodium tetrahydroborate to give Hg-O has been stu
died by using a continuous flow reaction system coupled with atomic fluores
cence spectrometric (AFS) detection. The quantitative reduction of Hg-II to
Hg-O takes place with a specific amount of sodium tetrahydroborate accordi
ng to the stoichiometric reaction of mercury with alkaline NaBH4. The compl
ete reduction of Hg-II-thiol complexes to Hg-O requires a molar excess of N
aBH4, of up to six orders of magnitude, depending on the type of complex. U
nder an appropriate excess of reductant, Hg-II and its thiol complexes are
not distinguishable giving the same AF molar response. The method allows th
e discrimination of Hg-II from Hg-II-thiol complexes without any preliminar
y separation. Applications to the indirect titration of thiols and to the d
etermination of the number of accessible-SH groups in pure ovalbumin sample
s are reported.