Donnan dialysis preconcentration coupled with ion chromatography and electrocatalytic oxidation for the determination of cyanide

An electrocatalytic amperometric detector for the ion chromatographic deter mination of CN- is described. A conducting composite that is based on a gra phite-loaded sol-gel material comprises the working electrode. The composit e is doped with a Ru-II metallodendrimer which is demonstrated to promote t he electrochemical oxidation of CN- at potentials positive of 0.5 V vs. Ag/ AgCl. In 6 mM NaOH, 0.05 M NaCl flowed at 1.0 ml min(-1), a 5-point calibra tion curve with the following linear least squares parameters is obtained o ver the range, 1.0-30 M CN-: slope, 24.2 +/- 0.1 nA M-1; intercept, - 6 +/- 2 nA; and r, 0.9997. The detection limit, 0.7 muM CN-, compares favorably to that obtained by amperometry at a silver electrode, 0.5 muM CN-, under c omparable experimental conditions. A 60-min preconcentration by Donnan dial ysis increases the sensitivity by a factor of 23.6. (C) 2000 Elsevier Scien ce B.V. All rights reserved.