Indirect determination of free cyanide in industrial waste effluent by atomic absorption spectrometry

An indirect method is described for the determination of free cyanide in industrial waste effluent samples by atomic absorption spectrometry (AAS). In an alkaline medium, cyanide forms a stable complex species Cu(BPTC)(CN)] (BPTC = 2-benzoylpyridine thiosemicarbazone), which can be extracted into a mixture of isobutyl methyl ketone-isopentyl alcohol (7 + 1) with an efficiency of greater than 98.5%. The extract can be analysed directly for copper (and hence indirectly for cyanide) by flame AAS. The calibration graph is linear up to 5.7 micrograms of cyanide per millilitre of solvent mixture and the limit of detection is 4.8 ng ml-1. A large number of foreign ions were found not to interfere with the proposed method.