SIMULTANEOUS QUANTIFICATION OF CYCLOSPORINE-A AND ITS MAJOR METABOLITES BY TIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROMETRY AND MATRIX-ASSISTED LASER DESORPTION/IONIZATION MASS-SPECTROMETRY UTILIZING DATA-ANALYSIS TECHNIQUES - COMPARISON WITH HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

Simultaneous quantification of cyclosporin A (CsA) and its major metabolite (AM1) in blood has been achieved using time-of-flight secondary-ion mass spectrometry (TOF-SIMS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF-MS). Previous investigations indicated that spectral interferences exist in the analysis of CsA blood samples by the above methods, In TOF-SIMS, interference is caused by overlap of the Ag-cationized internal standard, cyclosporin D (CsD), with the Ag-cationized metabolite, AM1. To resolve this interference and obtain quantitative information, cross-correlation analysis was applied to the TOF-SIMS data, Application of damped non-linear least squares curve-fitting was carried out to resolve an interference in the MALDI/TOF-MS data due to multiple cationization products (i.e. Na and K), Measurement of standard samples indicates that the minimum accuracy (95% confidence level) of the TOF-SIMS method was better than 9% for CsA and 13% for AM1 using only one standard curve. Similarly, the minimum accuracy of the MALDI/TOF-MS method was determined to be 14% for CsA and better than 25% for AM1. Blood samples obtained from transplant patients receiving CsA were analyzed by polyclonal fluorescence polarization immunoassay, highperformance liquid chromatography (HPLC), and by both TOF-MS methods, Both TOF-MS results for CsA and mono-hydroxylated CsA are in good agreement with the HPLC results.