DETECTION AND QUANTITATION OF GADOLINIUM CHELATES IN HUMAN SERUM AND URINE BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AND POSTCOLUMN DERIVATIZATION OF GADOLINIUM WITH ARSENAZO-III

A narrow-bore high-performance liquid chromatography method was developed for simultaneous separation of gadolinium diethylenetriaminepentaacetic acid (GdDTPA), the monomethylamide (GdDTPA-MMA) and the bis-methylamide (GdDTPA-BMA) in human serum and urine. The Gd complexes were detected at 658 nm after post-column derivatization with Arsenate III. The serum samples were ultrafiltrated, whereas the urine samples were centrifuged and diluted before analysis. With an injection volume of 10 mu l on a 2.1 mm ID reversed-phase column, the limit of detection of GdDTPA-BMA was calculated as 0.3 mu M and 1.1 mu M in serum and urine, respectively. The method was validated with respect to GdDTPA-BMA with a limit of quantification set to 2 mu M and 10 mu M in serum and urine, respectively. The best fit of the calibration curve was obtained using non-linear regression according to the equation Y = A + BX + CX(2) in the concentration ranges 2-800 mu M and 10-2000 mu M of GdDTPA-BMA in serum and urine, respectively. The precision of the method was found to range from 1 to 4% RSD. The recoveries of GdDTPA-BMA spiked in serum and urine were higher than 95% with an RSD equal to or less than 4%. The serum samples were stable for at least 5 months when stored at -70 degrees C, and the urine samples were stable for a least 6 months when stored at -20 degrees C.