Direct electrochemical sensing of phosphate in aqueous solution based on phase transition of calcium phosphate

Electrochemical determination of phosphate in aqueous solution attracts considerable interests in both biological and environmental fields. Due to the electrochemical inactive nature of phosphate, direct electrochemical detection of phosphate is still a highly challenging task. Herein we reported one direct electrochemical approach for the determination of phosphate based on the oxidation of coordinated OH during the phase transition of calcium phosphates (CaP). The mixture of amorphous calcium phosphate (ACP) and octacalcium phosphate (OCP, Ca8(HPO4)2(PO4)4•5H2O), which acts as the starting material for hydroxyapatite (Ca10(PO4)6(OH)2, HAP), was self-assembled on Nafion modified glassy carbon electrode (GCE). The as-prepared electrode (CaPs/Nafion) showed a distinct oxidation peak at 1.0 V vs Ag/AgCl in phosphate solution. The peak heights were directly proportional to the concentration of phosphate from 0.1 µM to 10 µM in the presence of 1 mM Ca2+. After comprehensive characterization of the CaPs/Nafion...