Preparative high-performance liquid chromatography for the purification ofnitrendipine and its dimethyl ester

Normal-phase preparative HPLC was applied to the purification of nitrendipi ne and its dimethyl ester from raw materials. For each separation, the chro matographic conditions were optimized by adjusting the sample size to achie ve an efficient purification with a yield of 99% in the shortest time. The contaminating impurities were removed in a single step by preparative chrom atography. This work demonstrates how gram quantities of analytically pure materials can be conveniently obtained using preparative HPLC.