Indirect determination of cyanide by single-column ion chromatography

The procedure was developed by modification of a pneumoamperometric method which uses the reaction of cyanide with iodine, since the final concentration of iodide is proportional to the initial concentration of cyanide. The sample is diluted so that the cyanide concentration is in the range of .5 - 10 ppm, acetate buffer is added to adjust the pH to a value between 4.5 and 6. Excess iodine is added in 95% ethanol, sample is diluted to constant volume and allowed to stand for ca 5 min. Small aliquots of sample are injected slowly into the ion chromatograph through a precolumn containing XAD-4 resin. The excess iodine is adsorbed on this precolumn. The ion chromatograph adsorbs the iodide reaction product on XAD-1 resin. The iodide is removed by elution with sodium phthalate. Retention time is ca 5 min. Contamination of the system may be prevented by the removal of the precolumn for iodine desorption using nitric acid in acetone and water. 2 figures, 3 tables.