A Fluorometric Method for Determining the Riboflavin Content of Foodstuffs

A number of chemical methods have been described for the determination of riboflavin (1-13). These methods are in general limited in use because, when applied to certain products, either they are not specific for riboflavin or all the riboflavin present is not recovered (2). In most cases the authors of papers presenting riboflavin methods have indicated that the methods are of limited application either by the titles of the publications or in the descriptions of the methods. The various methods have proved of value both in the limited application for which they were intended and in forming the basis for the more general method presented in this paper. Principle of Method-This method depends upon the following physical and chemical properties of riboflavin. (1) It fluoresces green when irradiated with blue light. (2) It is not destroyed by mild oxidation or by reduction. (3) It can be reduced to a nonfluorescing form with sodium hydrosulfite and reoxidized readily by shaking with air. (4) It is not reduced by stannous chloride. (5) The intensity of the fluorescence can be measured with a photoelectric cell. This method for determining riboflavin in an unknown solution is an indirect one. This is necessary owing to the fact that in foodstuffs other pigments and fluorescing substances are usually present and accompany riboflavin on extraction. The pigments interfere with the accuracy of the determination by absorbing a part of both the activating and the fluorescent light and hence cause the direct determination of riboflavin by measurement of fluorescence to be too low. The fluorescent substances interfere with the accuracy of the determination by fluorescing in the