Separation of anthraquinones by capillary electrophoresis and high-performance liquid chromatography

The separation and determination of twelve anthraquinones, viz. anthraquino ne 1, chrysphanol 2, aloe-emodin 3, alizarin ii, anthra-quinone-2-carboxyli c acid 5, purpurin 6, sennoside B 7, sennoside A 8, emodin 9, quinalizarin 10, rhein 11, and anthraflavic acid 12, were achieved by capillary electrop horesis (CE) and high-performance liquid chromatography (HPLC). Detection a t 260 nm with a buffer solution containing 30 mM sodium berate (adjusted to pH = 10.56 with 0.05N NaOH) and acetonitrile (9:1) in CE or with a linear gradient elution containing 20 mM KH2PO4 with 0.05% phosphoric acid (pH = 2 .91) and methanol in HPLC was found to be the most suitable approach for th is separation. Contents of six components (2, 3, 7, 8, 9, 11) in crude Rhei Rhizoma extract could easily be determined within 39 min by CE or 63 min b y HPLC. The effects of buffers on this separation and the validation of the two methods were studied.