Nickel(II)-selective membrane electrode based on macrocyclic ligand

A polystyrene-based membrane of 3,4:11,12-dibenzo-2,5,10,13-tetraoxo-1,6,9, 14-tetraazacyclohexadecane was prepared and investigated as a Ni2+-selectiv e electrode. The best performance was observed with the membrane having pol ystyrene to ligand composition of 1:6, which worked well over a wide concen tration range, 3.16 x 10(-6)-1.00 x 10(-1) mol L-1 with a near Nernstian sl ope of 30.7 mV per decade of activity between pH 2.5 to 7.0. The electrode exhibits a fast response time of 10s and was used over a period of 2 months with good reproducibility (S = +/- 0.2 mV). The selectivity coefficient va lues for monovalent, bivalent and trivalent cations indicate excellent sele ctivity for Ni2+ ions and it also works satisfactorily in a partially nonaq ueous medium of methanol and ethanol. The practical utility of the membrane sensor was observed in solutions contaminated with detergents, cetyltrimet hylammonium bromide and sodium dodecyl sulfate and the sensor was used succ essfully to determine nickel in electroplating waste.