DETERMINATION OF OROTATE BY LIQUID-CHROMATOGRAPHY WITH SENSITIZED LANTHANIDE ION LUMINESCENCE DETECTION

The phenomenon of sensitized lanthanide luminescence induced by orotate was investigated in order to develop a detection method for the determination of orotate after liquid chromatographic separation. The best results were obtained for Tb3+. Applying sensitized Tb3+ luminescence detection and reversed-phase ion-pair chromatography, the detection limits for orotate calculated from the chromatogram were improved by a factor of about ten compared with UV absorbance detection, despite dilution caused by the postcolumn addition of the Tb3+ solution. The limit of detection is 1 X 10(-8) M, linearity is found over three orders of magnitude of concentration (r = 0.998, n = 7) and the relative standard deviation at 1.1 X 10(-6) M orotate is 1.3% (n = 9). The proposed detection method provides better selectivity than absorbance detection for real samples. Normal orotate concentrations in human urine can easily be detected.