Related substances test and characterization of seratrodast in bulk drugs

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method for related substances test of seratrodast in bulk drugs has been developed. The separation was achieved on a ZirChrom Kromasil C₁₈ (200 mm×4.6 mm, 5 µm) column thermostated at 30 ºC using acetonitrile-0.05 M pH 3.0 potassium dihydrogen orthophosphate buffer (60:40, v/v) as a mobile phase. Wavelength was set at 267 nm. An external standard method using a dilution of the sample solution as reference was used for the purity test. The method was found to be simple, rapid, specific and sensitive with detection limit of 0.67 ng. A thorough study has been undertaken to identify and characterize an unknown impurity at a level over the identification threshold of 0.1 %, and its structure was elucidated as 7-(3,5,6-trimethyl-1,4-benzoquinone- 2-yl)-7-p-tolyl-heptanoic acid based on the data of MS, UV, IR and NMR spectra. Formation of the unknown impurity as well as the countermeasure was also discussed Colegio de Farmacéuticos de la Provincia de Buenos Aires