Determination of eldecalcitol in human plasma by SIL-IS UPLC-APCI-MS/MS method for pharmacokinetics study

Eldecalcitol is a novel analog of 1α,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] for the treatment of patients with osteoporosis. A highly sensitive and specific ultra-performance liquid chromatography coupled to atmospheric pressure chemical ionization tandem mass spectrometry (UPLC-APCI-MS/MS) technique featuring a lower limit of quantitation (LLOQ) as low as 5 pg/ml, has been established and validated for the rapid and accurate quantification of eldecalcitol in human plasma samples. Plasma samples were extracted by solid phase extraction (SPE). Stable isotope-labeled compound eldecalcitol-d6 was used as an internal standard (SIL-IS). The detection process was carried out utilizing Multi-Reaction Monitoring (MRM) mode, employing an atmospheric pressure chemical ionization (APCI) source operating in the positive ion modality. The target fragment ion pairs for eldecalcitol and SIL-IS were identified as m/z 508.6 transitioning to 397.4, and m/z 514.6 transitioning to 403.3, respectively. This method was validated regarding selectivity, LLOQ, linearity, accuracy and precision, recovery, matrix effects, dilution reliability, stability, carryover test, and incurred sample reanalysis (ISR). This methodology had been successfully employed to assess the pharmacokinetics (PK) profile of eldecalcitol in a clinical investigation.