A Rapid Photoelectric Method for the Determi- Nation of Glucose in Blood and Urine

The reduction of potassium ferricyanide to ferrocyanide by glucose has been used as the basis of several successful quantitative methods for glucose. In the most popular of these, the Hagedorn and Jensen (1) method, the excess of ferricyanide is determined by iodometric titration. In the Folin (2) micromethod, the ferrocyanide formed is converted to Prussian blue and measured calorimetrically. Only in the Hawkins and Van Slyke (3) method is use made of the fact that ferricyanide solutions are yellow and ferrocyanide colorless. In this method, glucose is estimated by measuring the time required completely to decolorize a ferricyanide solution. The Hawkins and Van Slyke procedure is easy and rapid. Its apparent lack of popularity is probably due to the fact that the exact end-point is difficult to determine and that any error made is irreparable. Furthermore, it does not lend itself to multiple determinations. The present author has been able to obviate the difficulties of the Hawkins and Van Slyke method and yet retain the principle involved. The resulting method is simple, easy, and accurate. In it, the diminution in the yellow color of an excess of ferricyanide by glucose is measured in a photoelectric calorimeter.