Abstract
The present study was carried out in order to investigate whether zeolite 13X (aperture 7.4 A˚) modification of a mercury electrode could provide discrimination against the interference from Cu2+ in the stripping determination of Zn2+ (utilizing the zeolite ion exchange capability, and the possibility for small differences in size and shape of hydrated Zn2+ and Cu2+ and hence the differences in zeolite affinity to these species). For this purpose a chemically modified electrode (CME) was constructed from a glassy carbon electrode, which was first coated with a zeolite 10X containing polymer matrix then subjected to mercury plating. The analytical characteristics of the CME were subsequently compared with those of a conventional thin mercury film electrode (TMFE). The comparison, which was based on analogous stripping experiments carried out using first the TMFE, then the CME, showed that stripping signals for Zn2+ as well as Cu2+ were obtained with both electrodes. However, the intermetallic compound interference observed for the CME Zn-response was much less pronounced than that encountered for the TMFE Zn-response, thus indicating that the zeolite modification provided a marked discrimination towards deposition of Cu2+. Subsequent standard addition experiments with 60 s depositions at −1200 mV revealed that the Zn-stripping signal obtained with the CME was linear for 0–3.5 μM Zn2+ in the presence of 10 μM Cu2+.
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