Extremely sensitive germanium stripping voltammetric determination with the use of a new Ge(IV)-catechol-V(IV)-HEDTA catalytic adsorptive system

Abstract

It was found that the addition of V(IV)-EDTA or V(IV)-HEDTA to a solution containing the Ge(IV)-catechol complex induced certain catalytic processes that significantly enhanced the adsorptive stripping voltammetric (AdSV) response of germanium. The catalytic enhancement achieved with V(IV)-HEDTA was determined to be 7.4 times higher than that in the presence of V(IV)-EDTA; the former oxidant was therefore selected for the development of a new, sensitive catalytic adsorptive stripping voltammetric (CAdSV) procedure of germanium quantification. The optimal CAdSV Ge(IV) response was obtained in a 0.05 M acetate buffer with a pH of 4.4, in the presence of 1.0⋅10−3 M of catechol, 1.0⋅10−3 M of V(IV) and 1.5⋅10−3 M of HEDTA. The sensitivity of the new method was 25.2 nA/nM and the catalytic response was linear within the range of 5·10−11 M to 2·10−8 M Ge(IV) for 80 s of accumulation. The limit of detection was found to be 1.0·10−11 M. The reproducibility was equal to 3.0%. Interferences from inorganic ions and surface-active substances were evaluated. The procedure was applied to determine Ge(IV) in mineral water. It was also shown that both the hanging mercury drop electrode and the non-toxic renewable silver amalgam film electrode can be applied for Ge(IV) quantification by means of the elaborated method, with similar performance.