Multisensor system for determination of polyoxometalates containing vanadium at its different oxidation states

The electronic tongue (ET) multisensor system has been employed for the detection of metal-oxygen cluster anions (polyoxometalates) containing vanadium (IV/V) atoms. Sensitivity of a variety of potentiometric chemical sensors with plasticized polyvinyl chloride and chalcogenide glass membranes was evaluated with respect to vanadyl/vanadate ions, decavanadate and a series of Keggin-type polyoxometalates (POM) such as α-[SiW11VIVO40]6−, α-[SiW11VVO40]5−, α-[BW11VIVO40]7−, α-[BW11VVO40]6−, α-[PW11VIVO40]5− and α-[PW12−nVnVO40](3+n)− (n = 1, 2, 3). Sensor's responses to vanadium complexes were evaluated in the pH range of 2.4–6.5 and a set of sensors appropriate for detecting a variety of vanadium species was selected. Such sensor array was able to distinguish different vanadium complexes allowing their simultaneous quantification in binary (V(IV)/V(V)) mixtures. The vanillyl alcohol oxidation with α-[SiW11VVO40]5− was monitored using ET to evaluate the capacity of proposed analytic system to detect simultaneously V(IV)/V(V) in POM under dynamic equilibrium. ET was demonstrated to be a promising tool for the discrimination and quantification of vanadium-containing POMs at different oxidation states. In particular, such a system could represent a significant interest for the mechanistic studies of redox reactions with POMs.