Multicomponent spectrophotometric assay of riboflavine and photoproducts.

A multicomponent spectrophotometric method has been developed for the simultaneous determination of riboflavine, formylmethylflavine and degradation products in photolysed solutions. It is based on partial separation of the photoproducts by chloroform extraction at pH 2.0 in a potassium chloride-hydrochloric acid solution and subsequent determination, in the aqueous phase, of riboflavine and formylmethylflavine at 445 and 385 nm. The chloroform extract containing lumichrome and lumiflavine is evaporated to dryness, the residue dissolved in acetate buffer (pH 4.5) and the products determined at 356 and 445 nm. The reproducibility of the method, based on the analysis of synthetic mixtures, is within +/- 5%. Absorption corrections for minor products and interfering substances have been proposed. Chromatographic, spectrophotometric and distribution coefficient data for riboflavine and photoproducts are reported. The method is specific, rapid and convenient for photodegradation studies of riboflavine and formylmethylflavine.