A good method for the analysis of available Cyanide is OIA 1677 or its essentially equivalent ASTM D6888. In this method weakly available metal cyanide complexes are reacted with a ligand exhange reagent, acidified, and the Hydrogen Cyanide gas liberated diffuses through a membrane into a dilute sodium hydroxide solution. The cyanide absorbed is quantitatively measured using an amperometric detector. Both OIA 1677 and ASTM D6888 are Flow Injection Analysis (FIA) methods. They are very precise, accurate, and essentially inteference free. The only known intereference is sulfide, and the potential interference can be eliminated to concentrations up to 50 mg/l by adding Bismuth to the acid reagent. These methods are very sensitive, detecting cyanide down to 2 ppb. The maximum range of the ASTM method is 400 ppb while OIA 1677 claims a range up to 5 ppm.
The ligand exchange reagents have been found to be unnecessary for most samples unless they happen to contain nickel or mercury above 2 mg/l.
The results generated using these methods are equivalent to Cyanide Amenable to Chlorination (CATC). Those familiar with analyzing CATC know that a total cyanide and a chlorinated sample cyanide must be analyzed making CATC actually two tests. With the above mentioned methods it is only one.