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

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 Ru(II) 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 muM CN(-), compares favorably to that obtained by amperometry at a silver electrode, 0.5 muM CN(-), under comparable experimental conditions. A 60-min preconcentration by Donnan dialysis increases the sensitivity by a factor of 23.6.