High-performance liquid chromatographic determination of the magnetic resonance imaging contrast agent Gadocoletate ion in human plasma, urine and faeces

Gadocoletate ion is a new paramagnetic intravascular contrast agent for magnetic resonance imaging (MRI). An high-performance liquid chromatographic method for assaying Gadocoletate ion in human plasma, urine and faecal samples is described. The analysis is based on the reversed-phase chromatographic separation of Gadocoletate ion from the endogenous components of the biological matrices and its detection during elution by ultraviolet light absorption at 200 nm. The selectivity of the method was satisfactory. The mean absolute recovery during the analytical sample preparation was greater than 87%. The precision, expressed as coefficient of variation (CV%) ranged from 0.29 to 5.90% and the accuracy, expressed as mean relative error (R.E.%) of the analytical method ranged from −3.7 to +7.1%. The detection limit in plasma and urine was 2.01 and 10.0 μg/mL (0.00203 and 0.0101 μmol/mL), respectively. The detection limit in homogenized faecal samples was 17.7 μg/g (0.0179 μmol/g). Stability studies were performed in human plasma and urine samples during the analytical cycle. Gadocoletate ion was shown to be stable in human plasma and in human urine when stored at about +4 °C for up 24 h, and after three freeze-thaw cycles. In addition, it was shown to be stable in samples of processed plasma and in diluted urine at about +4 °C for 48 h, and at room temperature for at least 24 h. As regards the long-term stability of Gadocoletate ion, the results of dedicated studies showed that Gadocoletate ion is stable in human plasma samples when stored at +4 °C for up to 30 days and at −80 °C for up to 90 days. Gadocoletate ion is stable in samples of human urine when stored at +4 °C for up to 30 days, and when stored at −20 °C and at −80 °C for up to 90 days. The method has been successfully validated in human plasma, urine and faeces and it has been shown to be precise, accurate and reliable.