Rapid and specific high-pressure liquid chromatographic assay for folic acid in multivitamin-mineral pharmaceutical preparations.

A high-pressure liquid chromatographic assay for folic acid in multivitamin-mineral pharmaceutical formulations was developed. The internal standard solution used for sample extraction contained a chelating agent, pentetic acid, for prevention of metal ion-catalyzed degradation of folic acid in th prepared samples. Samples were chromatographed using a paired-ion mobile phase (water-methanol, approximately 76:24; 0.015 M phosphate buffer, pH 7.0; and 0.3% tetrabutylammonium hydroxide) on a column packed with octadecylsilane bonded to microparticulate silica gel. Sample preparation was rapid, and total chromatographic time was approximately 20 min. The method was accurate, precise, and highly specific. Folic acid and the internal standard, methylparaben, were separated from other tablet components and a number of potential impurities and degradation products of folic acid.