Spectrophotometric assay of folic acid in pharmaceutical tablets VIA oxidative coupling

Abstract EN

A simple, accurate and sensitive spectrophotometric method for the determination of folic acid (FA) is described.

The method is based on the oxidative coupling reaction of FA with promethazine in the presence of sodium periodate to form a green water-soluble product, that is stable and has a maximum absorption at 600 nm.

A graph of absorbance versus concentration shows that Beer’s law is obeved over the concentration range of 25-600 ng of FA in a final volume of 25 ml (i.e., 1-24 ppm) with a molar absorptivity of (2.19x 104 L.mol'.cm'1), a Sandall sensitivity of (0.02 ng.cm'*), a relative error of (0.28-1.53%) and a relative standard deviation of (0.67-2.21%) depending on the concentration of FA.

The optimum conditions for full colour development are described and the proposed method has been applied satisfactorily to pharmaceutical tablets.