Determination of gold-based antiarthritis drugs and their metabolites in urine by reversed-phase ion-pair chromatography with ICP-MS detection.

A sensitive method for the determination of gold-based drugs auranofin, myochrysine, and their metabolites has been developed. These gold-containing compounds were separated by reversed-phase ion-pair chromatography with tetrabutylammonium chloride as the ion-pairing agent. Gold-specific on-line detection utilized inductively coupled plasma mass spectrometry (ICP-MS). The separation conditions of pH, methanol content, concentration of the ion-pairing agent and ionic strength have been investigated. The detection limit for auranofin, the last peak in the chromatogram, was 0.3 ng. These methods were applied to the analysis of gold-containing species in urine from arthritis patients on auranofin, myochrysine or solganol therapy. The recovery of the total gold-containing species from urine was greater than 90%. Dicyanogold(I) anion, [Au(CN)2]-, was detected in the urine of several patients.