OPTIMIZATION OF WAVE-FORMS FOR PULSED AMPEROMETRIC DETECTION OF CYANIDE AND SULFIDE WITH SILVER-WORKING ELECTRODE

A continuous potential pulse is applied to a silver-working electrode on a pulsed amperometric detector (PAD) for detection of free cyanide and sulfide. The moving phase is 0.1 M sodium hydroxide, 0.5 M sodium acetate and 5% (v/v) ethylenediamine mixture, and the flow rate is 0.7 mL/min. Optimized pulse conditions include a -200 mV (us. Ag/AgCl ref erence electrode) detection potential (E(d)) for 60 msec and 50 mV cle aning potential (E(c)) for 120 msec. The silver working electrode surf ace is not poisoned by cyanide or sulfide, and the PAD maintains longt erm stability without loss of sensitivity and reproducibility at these pulse conditions. The detection limit of cyanide and sulfide separate d by ion chromatography using an anion exchange column is 0.1 ppm and 0.05 ppm, respectively.