Preconcentration of cyanide from water by extraction with tributyltin hydroxide.

Samples of water (500 ml) are extracted with 25 ml of 0.25M tributyltin hydroxide in trichloroethylene, which is then stripped with 2M sodium hydroxide, the organic reagent being used for a further extraction of the water sample; this cycle is carried out four times. The combined sodium hydroxide extracts are then titrated with silver nitrate solution, with p-dimethylbenzylidenerhodanine as indicator. Mean recoveries are around 99%, and the limit of determination is 4 microg/l. Thiocyanate, sulphide, methanethiol and complex cyanides do not interfere.