Abstract
A simple and sensitive method for the analysis of cyanides by a modified Rankine apparatus and ECD-GLC has been developed. This method consists of 1) collecting free and combined (glycosides) cyanides separately by nitrogen-ventilated distillation at 0°C for 20 min and at 50°C for 2 h continuously, 2) changing cyanogen to cyanogen chloride by Chloramine-T, and 3) determination of cyanogen chloride by the head-space GLC method. Compared to the previous method, this proposal method has several advantages as follows : 1) free and combined (glycosides) cyanides can be determined simultaneously, 2) only a little amount of sample is used (0.2 g), 3) analytical procedure is simple and consumes shorter times in whole process, and 4) detection limit of cyanogen is less than 0.1 μg per test tube. Recovery test for free cyanogen, cyanogen derived from amygdalin and linamarin was carried out by using the powders of almond, red beans and Saltani beans with or without β-glucosidase. Recovery of free cyanogen was 92.0-101.5% with or without β-glucosidase. Recovery of amygdalin in almond powder was 90.0% with Almond emulsin β-glucosidase and 16.1% without the enzyme. Recovery of linamarin in red bean powder was 89.7% with linamarase and 13.2% without the enzyme. Recovery of linamarin in Saltani bean powder was 87.5-90.0% with or without β-glucosidase. Therefore, it is considered that the addition of enzyme is not necessary in case of cyanide-containing beans such as Saltani beans. The contents of cyanides in the imported beans were investigated by the proposal method. Contents of total cyanides were 45.0-76.9 ppm in Baby lima beans, 241.6-326.4 ppm in Butter beans and 327.2 ppm in Saltani beans while contents of free cyanogen were 0.5-3.1 ppm in Baby lima beans, 0.1-6.4 ppm in Butter beans and 3.3 ppm in Saltani beans.
