Fabrication and Comparison of Three Chromium(III) Selective Electrodes Prepared using N-(Imidazol-2-ylcarbamothioyl) Benzamide

In the present work, N-(imidazol-2-ylcarbamothioyl)benzamide was developed and employed as an ionophore for preparing three kinds of membrane chromium(III) selective electrode including electrode with liquid internal electrolyte (LIE), solid-state electrode (SSE) and coated wire electrode (CWE). Optimal membrane composition was determined to be 2% sodium tetraphenylborate, 58% dibutyl phthalate, 10% ionophore, and 30% polyvinyl chloride, resulting in Nernstian slope behavior. Linear concentration range was 1×10-3-7×10-6 mol L-1, 1×10-3-3×10-7 mol L-1, and 7×10-3-3×10-9 mol L-1 of chromium(III) with Nernstian slope 20.76, 21.79 and 19.05 mV/decade for LIE, CWE and SSE, respectively. An improvement was note in detection limit for SSE (3×10-9 M) and CWE (2×10-7 M) in comparison with LIE (7×10-6 M). Response times were approximately 5 seconds for LIE and CWE, and 4-6 seconds for SSE. The applicable pH range for the electrodes was 3.0-5.0. SSE and CWE demonstrated longer lifetimes of about 13 and 12 weeks, respectively, compared to LIE (11 weeks). These electrodes were utilized as indicator electrodes in the chromium(III) potentiometric titration with ethylenediaminetetraacetic acid.