Microdetermination of riboflavin and riboflavin 5′-phosphate by a catalytic photokinetic method

The method is based on the rate of photoreduction of both compounds by EDTA, which is a linear function of the concentration of riboflavin and riboflavin 5'-phosphate at low concentrations. The rate is monitored spectrophotometrically by the formation of ferroin, which is generated after reduction of iron(III) by the 1,5-dihydro form of the riboflavins in the presence of 1,10-phenanthroline. Linear calibration graphs are obtained between 3 × 10^?8 and 9.6 × 10^?7 M. The method is successfully applied to the determination of vitamin B₂ in pharmaceuticals, foods and rat tissues.