Simultaneous determination of memantine and amantadine in human plasma as fluorescein derivatives by micellar electrokinetic chromatography with laser-induced fluorescence detection and its clinical application.

A nonionic surfactant MEKC method with LIF detection was developed for the simultaneous determination of memantine, an anti-Alzheimer's disease agent, and amantadine, an anti-Parkinson's disease drug, in human plasma. Before analysis, the plasma samples were pretreated by liquid-liquid extraction with ethyl acetate, and derivatized with 6-carboxyfluorescein N-hydroxysuccinimide ester. The chemical derivatization is performed with 6-carboxyfluorescein N-hydroxysuccinimide ester in ACN - 5 mM pH 9.0 borate buffer (40:60, v/v) at 35 degrees C for 3 h. After the derivatization reaction, hydrodynamic injection (0.5 psi, 8 s) was used to introduce the derivatized solution, and the separation was performed in borate buffer (30 mM, pH 9.5) with the nonionic surfactant Brij-35 (0.07%, w/v); the separation voltage was 6 kV. The linear ranges of the method for the determination of memantine and amantadine in human plasma were over a range of 2.0-60.0 ng/mL. The detection limit was 0.5 ng/mL (S/N=3). This method was applied successfully to monitor the concentration of memantine or amantadine in patients with Alzheimer's disease or Parkinson's disease.