Technical Note

Cyanide assay based on its novel reaction with resorcinol and picric acid

G. Drochioiu1*, C. Oniscu2, V. Sunel1, K. Popa1, C. Cuciac1, D. Cozma1

1 Al. I. Cuza University of Iasi, 11 Carol I, RO-6600, Iasi, Romania
2 Gh. Asachi Technical University of Iasi, 71 Mangeron, Iasi-6600, Romania

Received 29 July 2002; accepted 15 December 2002


A highly selective spectrophotometric assay of hydrocyanic acid and cyanide ions based on their novel reaction with picric in the presence of resorcinol is described. Trace concentrations of cyanides in water and hydrocyanic acid collected in dilute sodium hydroxide solution are determined with a solution of 2 % sodium carbonate containing 110 g/ml of resorcinol and 229 g/ml of picric acid when a novel indophenol derivative of 2,6-dinitro-5-hydroxy-4- hydroxylamino-1-cyanobenzene is afforded. The formation of the novel dye was proved by elemental and spectral analyses. The mixtures is heated at 100oC for 30 min and, after cooling, the absorbance of the red-brown solution is read at 540 nm, where the blank showed a minimum absorption. Detection limit of this method has been evaluated to be below 0.01 g/ml CN-. The color system obeys Beers law in the range of 0.1 - 10 g/ml CN-, in which a maximum molar absorptivity of 4.53 x 103 l/mole.cm has been determined. Cyanide in air, in cigarette smoke, and in waste waters can directly be determined by this selective procedure, without its isolation.

Keywords: Cyanide; Picric acid; Resorcinol; Spectrophotometric assay

* Corresponding author
   E-mail : gabidr@uaic.ro