The colorimetric determination of cyanide in human food and animal feed.

The well-known Kröller method for the determination of cyanide requires the use of the harmful chemicals benzidine (carcinogenic) and bromine (toxic) in the colorimetric part; the analytical result depends strongly on the conduct of the liberation procedure. The substitution of barbituric acid and N-chlorosuccinimide for benzidine and bromine has been investigated. The reproducibility of both colorimetric reactions is similar, but the sensitivity of the barbituric acid colorimetry is approximately 50% higher. A reproducible liberation yield can be obtained by a proper control of the heating programme. The detection limit for cyanide in a solution is approximately equal to 10 micrograms/l.