Influence of Triton X-100 in stripping potentiometry

The influence of a saturated Triton X-100 layer on glassy carbon based mercury film electrodes when used for stripping potentiometry determination of mono-, di- and trivalent ions has been investigated. By using an electrode assembly, permitting medium exchange at a controlled potential, it has been possible to study, separately, the influence of such a layer on the electrolysis step and on the stripping step. The latter step has been carried out either by means of spontaneous chemical reactions using dissolved dioxygen (molecular oxygen) or mercury(II) as oxidants or by means of an applied constant current. Pseudopolarograms, registered in the presence and absence of a saturated layer during electrolysis followed by complete desorption of this layer prior to stripping, show that Triton X-100 had no effect on the monovalent T1(I) ion. The stripping signals obtained for the divalent ions Pb(II), Cu(II) and Cd(II) and trivalent ions Bi(III) and In(III) on Triton X-100 covered electrodes were found to be the same as those obtained from non-covered electrodes, provided the electrolysis potentials were decreased with approximately 0.15 and 0.40V, respectively. It was also found that a Triton X-100 layer, applied on the electrode after electrolysis and prior to stripping, had no effect on the magnitude of the stripping signals in the constant current mode. In the chemical oxidation mode the bismuth stripping signal increased with a factor of five when dissolved dioxygen was used as oxidant, the signal increase for the other elements being less than 30%. When mercury(II) was used as oxidant the increase in stripping signals was less than 20% for all elements studied. It was also found that Triton X-100 could be completely desorbed from the mercury film in acetate buffer containing 60% (v/v) ethanol in the whole potential range −0.10 to −1.70 V vs. SCE.