A Highly Selective Salicylate Electrode Based on Schiff Base Complexes of Cobalt(III)

The present article describes a new solvent polymeric membrane anion selective electrode based on Schiff base complexes of Co(III) as neutral carriers, which demonstrates excellent selectivity toward the salicylate ion (Sal−) and anti-Hofmeister selectivity sequence: salicylate>thiocyanate>perchlorate>benzoate>iodide>acetate> nitrite>nitrate>bromide>chloride>citrate>sulfate. The electrode exhibits a near-Nernstian potentiometric response in the range 1.0 × 10−1 ∼1.6 × 10−6 mol/L Sal− with a detection limit of 8.0 × 10−7 mol/L and a slope of −57.2 mV/pSal− in pH 5.5 of phosphate buffer solution at 20°. The response mechanism of the electrode was also studied with the a.c. impedance and spectroscopic techniques. The electrode can be applied to the determination of salicylate in human urine and pharmaceutical preparations with satisfactory results.