POSTCOLUMN REACTION SYSTEM FOR FLUORESCENCE DETECTION IN CAPILLARY ELECTROPHORESIS

A system for post-column derivatization in capillary electrophoresis h as been developed and evaluated. In this system, reagent is added thro ugh a porous tube connecting the separation capillary with a reactor c apillary. The reagent solution is driven by a regulated air pressure a pplied on the separation capillary inlet and the reagent vessel simult aneously. The system has been applied for the fluorescence detection o f amino acids using o-phthalaldehyde as reagent. The reactor capillary geometry and flow-rates were optimized with respect to sensitivity an d separation efficiency on the basis of measured reaction rate constan ts. A ten-fold increase in sensitivity could be obtained by using ''bu bble-cell'' capillaries instead of normal fused-silica capillaries for detection. Amino acids were separated in a pH 9.7 berate buffer. Plat e numbers in the order of 100 000 to 150 000 were obtained. Detection limits were typically between 2 . 10(-6) and 4 . 10(-6) mol l(-1), or 0.05 to 0.1 pmol injected. The method was applied to the determination of free amino acids in urine samples.