Synapt g2 si mass spectrometer

Stability studies were performed as described previously with some modifications for the specific compounds.^{18 (link), 38 (link)} Pooled human plasma was diluted to 50% with phosphate buffered saline at pH 7.5 and compounds were added to a final concentration of 100 μM in a volume of 100 μL. These solutions were incubated for the indicated times at room temperature in the dark. Compounds were incubated then extracted with 300 μL of LCMS grade acetonitrile. Debris was pelleted by centrifugation at 10,000 x g for 2 minutes. Extracts were evaluated by LCMS with a Waters Synapt G2-Si Mass Spectrometer in positive mode using a gradient starting at 25% acetonitrile then increasing to 80% acetonitrile over 8 minutes. Masses corresponding to the molecular ion [M+H]⁺, the sodium adduct [M + Na]⁺, and the dehydration product [M - OH]⁺ were generally observed, though this data varied by compound. The allylic acetate containing compounds were additionally examined for the presence of the de-acetylated form, which was detectable as described in the text at the retention time and mass of the corresponding pure standard. The integrated peak values for all three ions of the test compound, and its deacetylated form when applicable, were summed and compared to those of t = 0 minutes for each compound.