Fast and highly selective determination of cyanide with 2,2-dihydroxy-1,3-indanedione

A very simple, accurate, fast, selective and sensitive assay of cyanide based on its reaction with 2,2-dihydroxy-l,3-indanedione at basic pH is proposed. As little as 0.01 μg ml−1 of cyanide can be determined. The molar absorptivity may reach 5.1–8.0×104 l mol−1 cm−1 depending on the reaction conditions. Thus, 1 ml of sample solution is mixed with 500 μl of 5 mg ml−1 solution of 2,2-dihydroxy-1,3-indanedione monohydrate in 2% sodium carbonate. The absorbance of the purple color is measured at 510 nm in 1-cm glass cuvettes, 10–15 min after mixing the reagents. The procedure could also be used to identify free CN− in natural waters and hydrocyanic acid in the environment.