DETERMINATION OF VITAMIN-A IN DRIED HUMAN BLOOD SPOTS BY HIGH-PERFORMANCE CAPILLARY ELECTROPHORESIS WITH LASER-EXCITED FLUORESCENCE DETECTION

We have developed a high-performance capillary electrophoresis (HPCE) method to analyze the retinol (vitamin A) concentration as retinol-ret inol binding protein (holo-RBP) from microvolumes of serum (5-10 mu l) or one to two drops (similar to 20 mu l) of blood collected and air-d ried on blood collection filter paper. A 0.64-cm diameter disk was cut from the dried whole blood specimens and the samples were dissolved i n a pretreatment buffer and filtered. Filtrate was injected onto the H PCE column for analysis. The separation was carried out in a 60 cm x 5 0 mu m I.D. fused-silica capillary and the running voltage was 20 kV. A He-Cd laser with a wavelength of 325 nm was used for excitation, and the fluorescence of the holo-RBP complex was monitored at 465 nm by a photodiode. A virtual linear relationship was obtained for the retino l concentrations between HPCE and HPLC for 28 serum samples, 19 dried venous blood samples and 9 capillary dried blood spot samples, indicat ing that valid measures of serum retinol can be obtained from one to t wo drops of capillary blood collected on filter paper. The absolute de tection limit for retinol by HPCE is below 3 mu g/l. The method is ver y useful for vitamin A level screening, especially for children and pr emature new-born babies.