QUANTITATIVE MEASUREMENT OF CYCLOSPORINE-A IN BLOOD BY TIME-OF-FLIGHTMASS-SPECTROMETRY

Analytical methods have been developed for the detection and quantific ation of cyclosporin A (CsA) in blood using time-of-flight secondary-i on mass spectrometry (TOF-SIMS) and matrix-assisted laser desorption/i onization time-of-flight mass spectrometry (MALDI/TOF-MS). Linear cali bration curves were obtained for both methods in the range 25-2000 ng/ mL in whole blood. The limit of detection (LOD) and limit of quantific ation (LOQ) were determined to be 7 and 23 ng/mL, respectively, for th e TOF-SIMS method; the LOD and LOQ were 10 and 33 ng/mL, respectively, for the MALDI/TOF-MS method. Coefficients of variation ranged from 3 to 5% for the TOF-SIMS method and from 4 to 8% for the MALDI/TOF-MS me thod. Blood samples were also analyzed by a nonspecific method, fluore scence polarization immunoassay (FIPA), and by a specific method, high -performance liquid chromatography (HPLC). The TOF-MS results are in g ood agreement with the HPLC results, but not with the FPIA results. Th e TOF-MS methods can also provide information about CsA metabolites.