Fast Minimicroassay of Serum Retinol (Vitamin A) by Capillary Zone Electrophoresis with Laser-Excited Fluorescence Detection

In this paper, we present a fast minimicroassay of serum vitamin A by capillary zone electrophoresis with laser-excited fluorescence detection. A 60 cm x 50 µm I.D. fused-silica capillary was used for the separation, and the polymer coating was burned off 20 cm from the cathodic end to form a detection window. The buffer system consisted of 50 mM sodium phosphate plus 10 mM sodium chloride at pH 7.8. A helium-cadmium laser set at 325 nm was used for excitation, and the fluorescence of the vitamin A-retinol-binding protein complex was monitored at 465 nm using a photodiode. The stray and scattered radiation were removed by two special filters. Using this system, about 8 nl of serum sample were injected for direct analysis without any sample preparation. The analysis time for each sample was less than 6 min, and subfemtomole levels of vitamin A in human or animal blood could be easily detected. Therefore, the method is potentially useful for finger-prick vitamin A analysis, especially for babies and young children.