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.