Abstract
Colorimetric determination of folic acid presented in the U.S.P. can not be applied for the vitamin in multivitamin preparations owing to the inhibition of other vitamins, especially riboflavin and ascorbic acid, contained in the preparations. The present paper reports a modified colorimetric determination of folic acid achieved by the elimination of inhibiting substances based on the difference of adsorbability of acid clay depending on pH value.
