Deteсtion of trace cyanide in water by isonicotinic acid – pyrazolone – bispyrazolone polarography

To enhance the detection sensitivity of cyanide, a method was proposed for the determination of trace cyanide in water by using isonicotinic acid – pyrazolone – bispyrazolone polarography. Under optimized experimental conditions, cyanide reacted with chloramine T, isonicotinic acid, and pyrazolone, and bispyrazolone to form a stable blue dye, which produced a sensitive polarographic wave at a peak potential of -766 mV (vs. Ag/AgCl) on the dropping mercury electrode. The results showed that there was a good linear relationship between the cyanide concentration and the second-order derivative peak current (ip ) in the range of 0.32–60 μg·L–1, with an impressive detection limit of 0.08 μg·L–1. Bispyrazolone could effectively inhibit the decomposition of the blue dye and increase ip by 12%. The polarographic wave originated from the two-electron reduction of the carbonyl group on the pyrazolinone moiety of the blue dye, exhibiting an irreversible adsorptive characteristic. The method was successfully applied to the determination of cyanide in drinking water, groundwater, and surface water, with relative standard deviations of less than 4.5% and recovery rates ranging from 96.7 to 107%. The method significantly lowered the detection limit of cyanide and exhibited high precision and accuracy, making it suitable for the analysis of trace cyanide in water.