Simultaneous analysis of the enantiomers of verapamil and norverapamil in rat plasma by liquid chromatography-tandem mass spectrometry - Mateus, Fabiano Henrique; Lepera, José Salvador; Marques, Maria Paula; Boralli, Vanessa Bergamin; Lanchote, Vera Lúcia (Journal of Pharmaceutical and Biomedical, 2007)