Huperzine A is an alkaloid isolated from the Chinese plant Huperzia serrata. The absorption spectra and electrophoretic behaviour of the compound were studied. The compound shows two absorption maxima (λ max 230 and 310nm). The protonation constant was determined by spectrophotometry and capillary zone electrophoresis (CZE) and the recommended value is pK=7.70±0.07. A CZE method for the determination of Huperzine A in pharmaceutical tablets and serum has been developed. The method is based on

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... paration of the compound as a protonated species with electrophoretic mobility determined as 50.7 x 10 -9 m 2 V -1 s -1 . The optimal separation conditions were: acetate buffer (pH 4.60; 20 mM) as a background electrolyte, separation voltage 20 kV, temperature 25 º C, hydrodynamic injection 10 s and detection at wavelengths 230 and 310 nm. The analyses were run in an uncoated fused-silica capillary with total length of 47.5 cm (39.0 cm to the detector) and 75 µm I.D. The detection limit was found to be 70 µg/l. The method of Huperzine A determination was applied for analysis of various pharmaceutical products. The results were found to be in good agreement with the declared amount. The precision of the method is ±2.30%. A method for the determination of HupA in serum was also developed with detection limit ≈ 110 µg/l, which is applicable for pharmacokinetics and therapeutic drug monitoring of this compound.