Abstract
A stability-indicating photochemical method for the assay of riboflavin (RF) in photodegraded samples and aged vitamin preparations has been developed. It is based on photochemical conversion of RF to lumichrome (LC) in alkaline solution under controlled conditions of light intensity, temperature, pH, time of exposure, and distance. Under these conditions about two-thirds of RF is converted to LC and on the basis of the RF : LC ratio the concentration of RF can be determined in degraded solutions. The method involves the extraction of photolyzed solutions of RF (pH 2.0) with chloroform and determination of LC along with lumiflavin (LF) by a two-component spectrometric method at 356 and 445 nm. The method has been validated and the results of the assay of RF in photodegraded solutions compare well with those of the standard USP fluorimetric method. The recovery of the method is 99–101% and the precision is within 2%. The method is stability-indicating and can be applied to the assay of RF in photodegraded solutions and aged vitamin preparations. The method is specific compared to that of the USP fluorimetric method in which the degraded LC may interfere with the fluorescence emission of RF.
Highlights
Riboflavin (RF) is sensitive to light in aqueous solution [1,2,3]
The development of multicomponent spectrometric methods involving the assay of RF and its major photoproducts in degraded solutions [14, 15, 27] leads to the study of the kinetics of photodegradation reactions [14,15,16,17,18, 28]
The method has been validated under controlled experimental conditions and could be applied to the assay of RF in photodegraded solutions and aged vitamin preparations
Summary
Riboflavin (RF) is sensitive to light in aqueous solution [1,2,3] It is photodegraded by several pathways involving the excited singlet and excited triplet states [4,5,6,7,8,9,10]. The development of multicomponent spectrometric methods involving the assay of RF and its major photoproducts in degraded solutions [14, 15, 27] leads to the study of the kinetics of photodegradation reactions [14,15,16,17,18, 28]. The method has been validated under controlled experimental conditions and could be applied to the assay of RF in photodegraded solutions and aged vitamin preparations
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