Detection of metal ions in aqueous solution by voltohmmetry

A new electrochemical detection principle is described for the trace analys is of dissolved species which can be deposited at polycrystalline thin-film metal electrodes and which change the surface resistance of the electrode. Because the latter parameter is measured in dependence on the applied elec trode potential this method is called voltohmmetry. The preparation of the required thin-film electrodes and the experimental set-up is introduced and discussed. Typical voltohmmetric experiments are illustrated by measuremen ts of T1+/T1 at polycrystalline gold electrodes with a thickness of 15 nm. The analytical capabilities of this new approach are discussed. It is alrea dy possible to determine heavy metals such as T1(+), Pb2+ or Cd2+ in the ra nge of a few mug/L by surface resistance-potential measurements at thin-fil m electrodes with a simple cyclic technique. Further developments of voltoh mmetry are envisaged.