Quantitative determination of SC-68328 in dog plasma using flow injection and tandem mass spectrometry

A flow injection/tandem mass spectrometric assay was developed to quantitate SC-68328 in dog plasma using its stable isotopic analog [13C4]SC-68328 as an internal standard (IS). Since SC-68328, a manganese-based superoxide dismutase mimetic, is very unstable, very polar and adheres to silica-based high-performance liquid chromatographic columns, the analyte and IS were derivatized to their bis-isothiocyanate forms followed by a liquid-liquid extraction with methylene chloride and analyzed using positive ion electrospray mass spectrometric detection. SC-68328 was quantitated using the peak-height ratio of SC-68328 to its IS using MS/MS in the multiple reaction monitoring mode. The lower limit of quantitation of the assay was 0.25 microg ml(-1) SC-68328 in dog plasma with an inter-day precision of 11.8% and an accuracy of 113% (n = 12). Acceptable precision and accuracy were also obtained for concentrations in the calibration curve range (0.25-10 microg ml(-1) SC-68328 in dog plasma).