Polarographic determination of cyanide as contaminant in pralidoxime mesylate formulations

A method for the polarographic determination of cyanide as contaminant in pralidoxime mesylate (PM) formulations was developed. The volatile cyanide formed in the formulations was stabilized as tetracyanonickelate (TCN) anion complex after reaction with ammoniacal Ni(II) solution. The stable TCN anion complex (Kstb=1031) was determined by anodic stripping voltammetry at the hanging mercury drop electrode (HMDE). The polarographic signal was proportional to the cyanide concentration and the high concentration of PM did not interfere. The linear range of calibration was from 1.2 to 16 μg cyanide with r=0.998. The RSD was 1.3% (n=5) for 2.4 μg cyanide and a detection limit of 0.8 μg cyanide was calculated. The proposed method is adequate as a quality control of PM formulations.