Spectrophotometric determination of folic acid in pharmaceutical preparations by coupling reactions with iminodibenzyl or 3-aminophenol or sodium molybdate–pyrocatechol

Abstract

Novel coupling reagents are used for the simple and sensitive spectrophotometric determination of folic acid either in pure form or in its pharmaceutical preparations. The methods are based on the probable diazotization of the p-aminobenzoylglutamic acid obtained after reductive clevage of folic acid, followed by either coupling with iminodibenzyl to give a violet product with λ max of 580 nm or coupling with 3-aminophenol to produce an orange yellow-colored product with λ max of 460 nm. Sodium molybdate and pyrocatechol are used in the third method and the pale red-colored product formed has a λ max of 490 nm. The methods are highly reproducible and have been applied to the determination of folic acid in tablets and the results compare favorably with the official method. Common excipients used as additives in pharmaceutical preparations do not interfere in the proposed methods.