Simultaneous determination of ursodeoxycholic acid and its glycine-conjugate in serum as phenacyl esters using multidimensional liquid chromatography

A narrowbore high-performance liquid chromatographic (HPLC) method using co lumn switching is described for the simultaneous determination of ursodeoxy cholic acid (UDCA) and glyco-UDCA (GUDCA) from serum samples as their phena cyl esters. Serum samples were subjected to a preliminary clean-up using oc tadecylsilane reversed-phase extraction and derivatized with phenacylbromid e. The purification, fractionation and concentration of UDCA and GUDCA from the esterified serum sample were performed on-line by appropriate switchin g of columns. Limit of detection (LOD) of UDCA and GUDCA were 5 ng and the absolute mean recoveries averaged 84.4 +/- 8.2% and 85.2 +/- 8.4%, respecti vely. This method was successfully applied to the pharmacokinetic study of UDCA in rats and human.