Quantification of Risperidone and Paliperidone in Biological Matrices

Concentrations of RIS and the active metabolite, PAL, in plasma and bone marrow were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis as previously reported [17 (link)]. Briefly, RIS and PAL were extracted from both plasma and bone marrow via protein precipitation with acetonitrile. Separation was accomplished using a Waters XBridge C18 analytical column (3.0 x 50 mm, 3.5 μm). Mobile phase consisted of 0.1% formic acid in purified water (A) and 0.1% formic acid in acetonitrile (B). The flow rate was 0.4 mL/min, and heated to 60°C. Gradient elution was employed, with initial conditions 95% A and 5% B. Solvent composition was held at the initial conditions for 1.0 minutes, and then was ramped over the following 1.5 minutes to 95% B. Composition was maintained at 95% B for 1 minute. RIS and PAL were detected via an Agilent (Waldbronn, Germany) 6460 triple quadrupole mass spectrometer operated in positive ion MRM mode. The following transitions were monitored: RIS (411.2→191.0) and PAL (427.2→207.0). Significant differences between groups were determined by two-tailed T test using GraphPad Prism.