Identification of a degradation product in stressed tablets of olmesartan medoxomil by the complementary use of HPLC hyphenated techniques

An unknown degradation product (DP-1) increased in olmesartan medoxomil (OLM) tablets stored at 40 °C/75% r.h., reaching 0.72% after 6 months. The molecular weight and fragment information obtained by LC–MS suggested that DP-1 was a dehydrated dimer of olmesartan (OL) and the presence of ester carbonyl group was indicated by solvent-elimination LC–IR analysis. LC–1H NMR confirmed the structure of DP-1 as an esterified dimer of OL. Rapid and accurate identification of the degradation product was achieved by the complementary use of HPLC hyphenated techniques without complicated isolation or purification processes.