DETERMINATION OF GERMANIUM BY POTENTIOMETRIC STRIPPING ANALYSIS AND ADSORPTION POTENTIOMETRIC STRIPPING ANALYSIS

Potentiometric stripping analysis was applied to determination of germanium(IV) in 0.2M NH3-NH4Cl (pH 8.4) buffer solution at -1.8 V (vs. Ag/AgCl), with dissolved oxygen or Hg(II) as oxidant. The sensitivity was 8.5 x 10(-9) M in the presence of 2.0 x 10(-5) M Hg(II) with plating for 15 min after deaeration for 20 min. Cyclic voltammetry revealed that Ge(IV) --> Ge at the surface of the mercury-film electrode in a one-step irreversible reduction reaction, and the Ge at the electrode was oxidized by dissolved oxygen in the solution. The presence of complexing agents such as Alizarin Red (ARS), which forms a Ge(IV) complex adsorbed at the electrode, improved the sensitivity by one order of magnitude. The presence of adsorption was revealed by the temperature coefficient, the electrocapillary curve and cyclic voltammetry. Ge-containing samples were analysed by the proposed methods and agreement with the results obtained by other methods was excellent.