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-mu-g 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.