Simple picrate method for the determination of cyanide in cassava flour

A simple picrate method was used to quantify the cyanide contents of food samples. The cyanide in the food samples reacted with hot 20% HCl solution to produce hydrogen cyanide vapour which reacted with alkaline picrate test strips to form red colour on the test strips. The red coloured complex on the strips was extracted with 50% ethanol solution and the absorbance of the extract was measured at 510nm using a spectrophotometer. The method was reproducible and cyanide as low as 1 microgram could be determined. Cyanide levels of all the cassava varieties tested were higher than the 10ppm WHO safe level. Recovery of cyanide from acyanogenic foods fortified at levels of 5 and 10mg KCN/10g were 98.6% and 99.1% respectively. The picrate method is simple and useful for routine determination of cyanide content of cassava flour.

 O Nwokoro, J.C Ogbonna, G.N Okpala