A simple cyanide test kit for water and fruit juices

Abstract

A sensitive, selective, rapid, and user-friendly field test kit was developed for the determination of cyanide. The method was based on a reaction to generate hydrogen cyanide from the solution containing cyanide by reaction with sulfuric acid in a specially designed reaction bottle. The gaseous hydrogen cyanide diffused and was collected on a paper strip impregnated with p-nitrobenzaldehyde and o-dinitrobenzene in sodium hydroxide. Hydrogen cyanide reacted with p-nitrobenzaldehyde to form an intermediate p-cyanobenzadehyde cyanohydrin, which reacted with o-dinitrobenzene to give a purple compound, the dianion of o-nitrophenyl hydroxylamine. The intensity of the purple color depended on the concentration of cyanide in the test solution. The developed field test kit could be used for the detection of cyanide as low as 0.01 mg l⁻¹ within 10 min. The cyanide field test kit was applied to determine cyanide concentrations in natural water and commercial fruit juices with good accuracy as validated by using the APHA/AWWA/WEF standard method 4500-CN⁻.