Anion-selective light-addressable potentiometric sensors (LAPS) for the determination of nitrate and sulphate ions

Abstract

The technology of fabrication of anion-selective light-addressable potentiometric sensors (LAPS) by using a solid-state microelectronic device integrated with an ion-recognition membrane has been elaborated. The nitrate sensor with ion-exchange membrane exhibits a linear response interval of 3×10 −5 to 1×10 −1 mol/l NO 3 − with an ionic sensitivity of 58±2 mV/pNO 3. The detection limit was found to be 1×10 −5 mol/l of nitrate ions and the working pH interval of the sensor is 2.0–11 for 10 −2 mol/l NO 3 −. The sensor has a high selectivity for nitrate over chloride, sulphate, hydrogen phosphate and acetate ions with selectivity coefficients, K NO 3/X , of 7×10 −3, 1×10 −3, 2×10 −4 and 5×10 −3, respectively, and a response time of about 1 min. The SO 4-LAPS with polymeric membrane containing neutral sulphate ionophore demonstrates a sensitivity of 26±1 mV/pSO 4 in a concentration range of 3×10 −6 to 1×10 −2 mol/l with a reasonable selectivity over chloride, hydrogen carbonate and hydrogen phosphate ions. Selectivity coefficients, K SO 4/X , were found to be 0.6, 0.15 and 0.03, respectively.