The synthesis of 1,4-diaza-2,3;8,9-dibenzo-7,10-dioxacyclododecane-5,12-dione and its use in calcium-selective carbon paste electrodes

A synthetic procedure has been developed for the preparation of 1,4-diaza-2,3;8,9-dibenzo-7,10-dioxacyclododecane-5,12-dione. A carbon paste electrode based on the new macrocyclic diamide was constructed for Ca2+ determination. The calibration graph was linear over a wide concentration range (1.3 x 10(-6)-3.2 x 10(-3) M) with a near Nernstian slope of 32 mV decade(-1). The limit of detection is 7.9 x 10(-7) M (0.032 ppm). Selectivity coefficients were tabulated and the working pH range was determined. It has a fast response time of < 10 s and can be used for at least 3 months without any considerable divergence in potentials. The electrode was successfully applied to the determination of Ca2+ ions in a pharmaceutical preparation.