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.