Monohydrogen phosphate selective electrode based on a synthetic hydrotalcite

An ion-selective electrode (ISE) for monohydrogen phosphate, based on a dispersion of Mg/Al hydrotalcite-like compound particles into a polymeric membrane of polyvinyl butyral, in the coated-wire configuration, is described. The inorganic ionophore was ad hoc synthesized and characterized. The electrode showed a Nernstian response towards monohydrogen phosphate independently from the pH of the solution in the range 4.5–7.8 with a linearity range from 5.0 × 10−5 to 2.0 × 10−2 M and a limit of detection of 3.0 × 10−5 M. The response time varied from 10 to 25 s. Potentiometric selectivity coefficients for the proposed sensor were evaluated over several mono- and divalent anions, chosen among the most common ones. The results pointed out a reasonably good selectivity for monohydrogen phosphate. A successful application of the developed ISE for phosphate determination in hydroxyapatite samples using direct potentiometry is presented.