SEPARATION OF HISTORICAL DYES USING CAPILLARY ELECTROPHORESIS WITH LASER-INDUCED FLUORESCENCE DETECTION

In this study, the separation properties of alizarin, purpurin, carmin, and morin were explored using capillary electrophoresis (CE). A 30-cm capillary (10 mu m i.d.) and an applied voltage of 16-20 kV was used to separate the dyes prior to post-column detection in a sheath flow cuvette using laser-induced fluorescence (LIF). Two lasers were used for excitation: a 488 nm argon ion laser and a 407 nm diode laser (50 mW). Samples were electro-kinetically injected (10 kV for 5 s) into the capillary. Detection limits for alizarin, purpurin, carmine, and morin (n = 3) were determined to be 1.0, 2.1, 3.4, and 0.3 mu g L-1, respectively. The extraction of alizarin from two powdered sources of Rubia tinctorum (madder) was also achieved using dimethyl sulfoxide (DMSO) that was heated gently prior to dilution with a 20-mM borate buffer. Concentrations of alizarin in two sources of powdered madder root were found to be 10.2-10.7 mg g(-1).