Picrate paper kits for determination of total cyanogens in cassava roots and all forms of cyanogens in cassava products

The simple semiquantitative picrate method for the determination of total c yanogens in cassava flour has been modified by increasing the concentration of the picrate solution used to make up the picrate papers, such that a li near Beer's Law relation between absorbance and cyanogen content is obtaine d over the range 0-800mg HCN equivalents kg(-1) cassava. The method has bee n adapted to determine the total cyanogen content of cassava roots and the results compared using the picrate method and the acid hydrolysis method fo r six different roots from five cultivars. The agreement between the result s is satisfactory. The simple method for determination of total cyanogens i n cassava roots in the field is available in kit form. The methodology has been modified to allow determination of the three different forms of cyanog ens present in cassava flour, viz HCN/CN-, acetone cyanohydrin and linamari n. HCN/CN- is determined by the picrate method in which cassava flour is re acted with 0.1 M sulphuric acid for 3h at room temperature. HCN/CN- plus ac etone cyanohydrin is also determined by the picrate method after treating c assava flour with 4.2 M guanidine hydrochloride at pH 8 for 3 h at room tem perature. A comparison has been made of the amounts of the three cyanogens present in six cassava flour samples using the semiquantitative picrate and the acid hydrolysis methods. The agreement between the two methods is sati sfactory, which shows that the new methodology works well. The picrate meth od for determination of the three cyanogens in cassava flour is also availa ble as a kit. (C) 1999 Society of Chemical Industry.