CYCLIC POLYAMINE IONOPHORE FOR USE IN A DIBASIC PHOSPHATE-SELECTIVE ELECTRODE

A cyclic polyamine, 3-decyl-1,5,8-triazacyclodecane-2,4-dione (N-3-cyc lic amine), was used as the ionophore for a dibasic phosphate-selectiv e electrode. This electrode exhibited a linear response between 1.0 mu mol/L and 0.1 mol/L dibasic phosphate activity with a near-Nernstian slope of similar to-29 mV per activity decade. The electrode selectivi ty for dibasic phosphate over other commonly occurring anions was eval uated. A mechanism for the selectivity of the electrode toward HOP42- ions is postulated to be a function of the size and charge of the N-3- cyclic amine ionophore relative to the size and charge of HPO42- ions. The electrode's superior selectivity and sensitivity make possible th e direct measurement of phosphate activity in a wide variety of applic ations.