Separation and determination of alpinetin and cardamonin in Alpinia katsumadai Hayata by flow injection–micellar electrokinetic chromatography

A simple, rapid, and accurate method for the separation and determination of alpinetin and cardamonin in Alpinia katsumadai Hayata was developed by combination of flow injection (FI)–micellar electrokinetic chromatography (MEKC) for the first time. The analysis was carried out using an unmodified fused-silica capillary (50 μm i.d.; total length 13.6 cm; effective length 10.3 cm) and direct ultraviolet (UV) detection at 214 nm. The sample throughput was 11–24 samples per hour using the background electrolyte (BGE) containing 4 mM sodium borate–8 mM NaH2PO4 (pH 8.1)–8 mM sodium dodecyl sulfate (SDS)–19% (v/v) ethanol. The repeatabilities (n = 4) reached relative standard deviation values (R.S.D.) of 3.0% and 2.5% for the peak areas and 2.5% and 3.1% for peak heights of alpinetin and cardamonin, respectively. Regression equations revealed linear relationships (r2: 0.9993–0.9994) between the peak area of each analyte and the concentration. Recoveries were in the range 90–92% and 99–105% for alpinetin and cardamonin, respectively.