Use of Cobalt(II) and Chromium(III) Metal based Schiff-Base Complexes for the Preparation of Potentiometric Sensors to Determine Bromide at Ultra-Low Concentrations

Abstract

Co(II) and Cr(III) salicylidenic Schiff-base based complexes as novel ionophores were evaluated for the fabrication of bromide-selective electrodes. By incorporating a cation excluder along with various plasticizers (dibutyl phthalate, dioctyl phthalate, 1-chloronapthalene), optimized sensors (CoC7 and CrC7) exhibiting near-Nernstian slopes being 59.4±0.07 and 59.2±0.04 mV decade-1, with a broad linear range (1×10-2 to 6.0×10-7 and 1 × 10-2 to 8.7 × 10-7 mol·L-1), with low detection limits (5.5±0.13×10-7 and 6.5±0.07 ×10-7 mol·L-1) respectively. Selectivity coefficient values of order 10-1 or less indicate that the proposed electrodes have superior selectivity for bromide ion over various interfering anions. The developed bromide electrodes demonstrated robust performance within a pH range of 4.0 to 9.0, as well as showed sufficient shelf life (4 and 5 weeks) with up to 20 % (v/v) non-aqueous tolerance and quick response times (12 and 16 s). These electrodes also served as indicator electrodes in the potentiometric titration of bromide ions against AgNO3 and were used in the determination of bromide ion concentration in water samples.