HPLC STUDY OF THE IMPURITIES PRESENT IN DIFFERENT URSODEOXYCHOLIC ACID PREPARATIONS - COMPARATIVE-EVALUATION OF 4 DETECTORS

The use of HPLC with different detectors has been investigated for the analysis of bile acid impurities present in four different commercial ly available ursodeoxycholic acid preparations. The bile acids were ef ficiently separated by C18 reversed-phase HPLC using methanol-water (3 :2, v/v) as the mobile phase. The detectors used for bile acid detecti on were: UV at 200 nM refractive index (RI) and an evaporative light s cattering mass detector (ELSD II). A prederivatization method with the formation of a fluorescent naphthacyl ester has also been used. GC-MS analysis of Me-TMS bile acid derivatives was included as a reference method. The four ursodeoxycholic acid samples were 98-99% pure. The ma in impurities present in the samples were chenodeoxycholic acid and to a lesser extent lithocholic acid. Only one sample was found to be alm ost 100% pure using all the detectors. Significant agreement of the da ta was found between RI, ELSD II detectors and the fluorescent method; the UV detector was unsuitable for use in this method. The analytical performances of the four detectors for bile acid analysis are reporte d and discussed. When the four-detector data were compared with the GC -MS method, reasonable agreement resulted. Discordant results were fou nd in the quantitation of trace impurities like lithocholic acid and/o r other minor bile acids present in amounts less than 0.1%.