A round robin test for the total cyanide determination of complicated wastewater samples

A round robin test between seven universities was carried out for the determination of total cyanide in complicated wastewater samples by Japanese Industrial Standards and other analytical methods. Six kinds of waste samples obtained from university laboratories and a tap water sample were prepared. Relative standard deviation of the analytical data for these samples by the Japanese official method were within ±10%. Interference of organic compounds, residual chlorine at low concentration or sulfide on the total cyanide determination was eliminated by the addition of ascorbic acid or zinc acetate at distillation. However, in the presence of residual chlorine at high concentration, recovery of total cyanide was only 4050% even by ascorbic acid addition and moreover cyanide ion was formed by the addition of hydroxylamine hydrochloride. It was found that cyanide compounds such as NH4Fe[Fe(CN)6] which are not easily decomposed, can be analyzed quantitatively by an increase of EDTA addition by three times at distillation.