Figure 3: The mass spectra of (a)amantadine 2380.0 ng mL-1 (b)memantine, 1190.0 ng mL-1, (C) mixture of memantine, 119.0 ng mL-1 (analyte) and amantadine, 2380.0 ng mL-1 (IS) in 50% aqueous solution of acetonitrile containing 0.1% formic acid.