Electrochemical Formation of 11-Molybdophosphate Anion at the Nitrobenzene/Water Interface and Its Applicability to the Determination of Orthophosphate Ion

Abstract

Transfer of the hexamolybdate ion, Mo₆O₁₉²⁻, at the nitrobenzene(NB)/water(W) interface was studied by ion-transfer voltammetry. The Mo₆O₁₉²⁻ ion decomposed immediately after being transfered from NB to W. In the presence of orthophosphate ions in the weakly acidic W phase (pH 3.1), molybdophosphate anions, i.e. [H₃PMo₁₁O₃₉]⁴⁻, were formed at the interface. A well-defined voltammetric wave due to the transfer of complex anions from W to NB was observed; the peak current was proportional to the bulk concentration of orthophosphate ions. Thus, the NB/W interface containing Mo₆O₁₉²⁻ in NB can function as an ion-selective electrode surface for a voltammetric determination of orthophosphate ions.