Novel thiocyanate-selective membrane sensors based on di-, tetra-, and hexa-imidepyridine ionophores

Abstract

Potentiometric thiocyanate-selective sensors based on the use of three synthesized di-, tetra-, and hexa-imidepyridine derivatives as novel anionic neutral ionophores in plasticized poly(vinyl chloride) (PVC) membranes are described. The sensors exhibit significantly enhanced response towards thiocyanate ions over the concentration range 5×10-6 to 1.0×10-2M with a lower detection limit of 0.3μg ml-1 and slopes ranging from -55.6 to -58.3mV per decade. Fast and stable response, good reproducibility, long-term stability, applicability over a wide pH range (2-8) and high selectivity for SCN- ion in the presence of 18 common anions are demonstrated. The sensors are used for direct potentiometric measurements of thiocyanate ions over the concentration range 0.2-580μg ml-1 and for monitoring sequential titration of some metal ions (e.g. Ag+, Tl+, Cu2+, Pb2+) in binary and ternary mixtures. Sequential binding of these metal ions with SCN- ensures share stepwise titration curves with consecutive end point breaks at the equivalent points. Recoveries of 98.5-99.1 ± 0.3% are obtained for metal ion concentrations of 0.06-4mg ml-1. © 2003 Elsevier Science B.V. All rights reserved.