Ammonium ion sensor based on SiO2/ZrO2/phosphate- NH4+ composite for quantification of ammonium ions in natural waters

Abstract

Ion selective-electrode was constructed and evaluated for determination of ammonium ions in natural waters. The electrode consists of paste carbon with the composite SiO2/ZrO2/phosphate-NH4+ obtained through sol-gel process. The electrode exhibits a sub-Nernstian response for ammonium concentrations between 7.7×10-7 and 4.0×10-2 mol L-1 and a detection limit of 1.58x10-7 mol L-1 (8.5×10-3 ppm). The electrode response for ammonium was fast (1 minute). The selectivity coefficients KpotA,B for several ions usually present in natural waters were determined applying the matched potential method. The potentiometric method with the ion selective electrode was validated by the Berthelot method (standard method), through the determination of ammonium ions in natural waters. The ion selective-electrode proved suitable for routine quality control of natural waters by potentiometry. ©2007 Sociedade Brasileira de Química.