Liquid chromatographic determination of pindolol and related compounds in raw materials

A liquid chromatographic method for the assay of pindolol and related compounds in the bulk drug has been developed. The method resolves 6 known and several unknown impurities from the drug and each other by using a nitrile column, an acetonitrile-sodium acetate buffer (35 + 65), and a UV detector set at 219 nm. Minimum quantifiable amounts of impurities are 0.02% or less relative to the drug. Ten lots of pindolol raw material were evaluated for purity and drug content. Total levels of impurities in these samples, quantitated against pindolol, ranged from about 0.03 to 0.24%. Assay results were within the range of 98.5 to 101.5%.