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

An electrocatalytic amperometric detector for the ion chromatographic determination of CN− is described. A conducting composite that is based on a graphite-loaded sol–gel material comprises the working electrode. The composite is doped with a RuII metallodendrimer which is demonstrated to promote the 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 calibration curve with the following linear least squares parameters is obtained over 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 μM CN−, compares favorably to that obtained by amperometry at a silver electrode, 0.5 μM CN−, under comparable experimental conditions. A 60-min preconcentration by Donnan dialysis increases the sensitivity by a factor of 23.6.