Determination of cyanocobalamin by thermal decomposition of the cyano group using an ion-selective electrode

A method for the simultaneous determination of cyanocobalamin, cobinamide (Factor B), and hydroxocobalamin in the solid state is described. The method is based on heating at 120 degrees for cobinamide and at 140-145 degrees for cyanocobalamin (15-20 min). The cyano content in the sample is distilled as hydrocyanic acid, trapped in 0.1 M potassium nitrate at pH 12-13, and determined by means of the cyanide ion-selective electrode. The error of this method, statistically established, does not exceed +/-3%.