Separation of fluorescein dyes by capillary electrophoresis using beta-cyclodextrin

A capillary electrophoresis method for the separation and determination of five synthetic dyes used in pharmaceutical preparations, cosmetics and as f ood additives is described. The dyes, fluorescein, dichlorofluorescein, Ros e Bengal, erythrosine and eosine are well separated in less than 12 min usi ng an electrolyte of 50 mM phosphate buffer (pH 7.5), 10 mM beta-cyclodextr in and 5 % (v/v) methanol. A linear relationship between concentration and peak area for each dye was obtained in the concentration range 0.3-500 mu g ml(-1), with a correlation coefficient greater than 0.999. Intra-and inter -day precision of about 0.2-2.6 % RSD (n = 11) and 4.9-9.7 % RSD (n = 30), respectively, were obtained. The method has been used for determining the p urity of fluorescein and erythrosine in practical samples.