Determination of release limits: a general methodology.

Release limits of drug dosage forms are defined as the bounds on the potency at which an individual lot can be released for marketing which will ensure that it remains within registered limits throughout its shelf life. A statistically based method is described for calculating release limits for any type of dosage form and any parameter for which the rate of change with time is predictably uniform and linear. When the mean release assay result for a specific product lot is at or within the calculated release limit bounds, assurance is provided at the specified confidence level that the average assay results obtained at any subsequent time within the shelf life will remain within registered limits.

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.