Polymeric Membrane and Solid Contact Electrodes Based on Schiff Base Complexes of Co(III) for Potentiometric Determination of Perchlorate Ions

Abstract

New PVC based polymeric membrane electrodes (PME) and coated glassy carbon electrodes (CGCE) based on synthesized Schiff base complexes of Co(III); [Co(Salen)<TEX>$(PBu_3)_2$</TEX>]<TEX>$ClO_4$</TEX>, [Co(<TEX>$Me_2$</TEX>Salen)<TEX>$(PBu_3)_2$</TEX>]<TEX>$ClO_4$</TEX>, [Co(Salen)<TEX>$(PBu_3)H_2O$</TEX>]<TEX>$ClO_4$</TEX>; as anion carriers for potentiometric determination of <TEX>$ClO_4\;^-$</TEX>were studied. The PME and also CGCE electrodes prepared with [Co(Me2Salen)<TEX>$(PBu_3)_2$</TEX>]<TEX>$ClO_4$</TEX> showed excellent response characteristics to perchlorate ions. The electrodes exhibited Nernstian responses to <TEX>$ClO_4\;^-$</TEX> ions over a wide concentration range with low detection limits (<TEX>$1.0 {\times} 10^{-6}\;mol\;L^{-1}$</TEX> for PME and <TEX>$9.0 {\times} 10^{-7}\;mol\;L^{-1}$</TEX> for CGCE). The electrodes possess fast response time, satisfactory reproducibility, appropriate lifetime and, most importantly, good selectivity toward <TEX>$ClO_4\;^-$</TEX> relative to a variety of other common inorganic anions. The potentiometric response of the electrodes is independent of the pH in the pH range 2.5-8.5. The proposed sensors were used in potentiometric determination of perchlorate ions in mineral water and urine samples. The interaction of the ionophore with perchlorate ions was shown by UV/Vis spectroscopy.