Determination of cyanide using a microdiffusion technique and potentiometric measurement

Abstract

A rapid, accurate and simple method for cyanide determination using microdiffusion as a separation technique, followed by potentiometric measurement of CN^– in the inner chamber of a microdiffusion cell is proposed. The optimum conditions for potentiometric measurement of CN^– in the microdiffusion cell (stirring, response time and effect of polishing the ion-selective electrode membrane) were studied at different concentrations of cyanide. The precision, linear response of the electrode against CN^– concentration and detection limit were established. The conditions for microdiffusion (temperature, time and pH of HCN released in the outer chamber) were also studied at different CN^– concentrations. The optimum conditions determined for the microdiffusion process were 25 °C, 2 h and pH 5.

The calibration graph for the cyanide electrode was linear between 10^–3 and 10^–6M CN^–. The detection limit obtained was 0.018 mg l^–1 of CN^–. The reproducibility of the electrode response for 1.76 mg l^–1 of CN^– was 1.97%(relative standard deviation).

The method may be used in water analysis, for the determination of “free cyanide,” and for the determination of CN^– in solid or liquid samples that are able to liberate HCN under the microdiffusion conditions established.