CHARACTERISTIC FEATURES OF THE THROUGHOUT-CAPILLARY TECHNIQUE OF IN-CAPILLARY DERIVATIZATION IN CAPILLARY-ELECTROPHORESIS

Characteristic features of the throughout-capillary technique of in-ca pillary derivatization for capillary electrophoretic analysis were exp lored using a rapid derivatization model. Selected amino acids (phenyl alanine, glycine and glutamic acid) were converted to their OPA deriva tives, while they were moving through an electrophoretic solution cont aining OPA in the electric field, and the resultant OPA-amino acids we re concurrently analyzed by zone electrophoresis with UV detection. A deep trough appeared based on sample-reagent displacement, and the bas e line was noisy and drifty, especially at high reagent concentrations . Peaks were fronting and peak width varied among amino acid species, presumably due to the variation of the difference in velocity between an amino acid and its OPA derivative. However, the throughout-capillar y technique is the simplest of all techniques of pre-capillary and in- capillary derivatizations, and there was good linearity between relati ve peak area and amino acid concentration. The quantification was repr oducible with R.S.D.similar to 3.5%. The rate constant of the derivati zation reaction could be roughly estimated by plotting logarithm of am ino acid concentration vs. reaction time. The obtained values were app roximately identical with the values obtained by the zone-passing tech nique. This paper also compares this technique with other techniques o f in-capillary derivatization with respect to peak area, signal-to-noi se ratio and column efficiency. (C) 1998 Elsevier Science EX All right s reserved.