Characteristic features of the throughout-capillary technique of in-capillary derivatization in capillary electrophoresis

Characteristic features of the throughout-capillary technique of in-capillary derivatization for capillary electrophoretic analysis were explored using a rapid derivatization model. Selected amino acids (phenylalanine, glycine and glutamic acid) were converted to their OPA derivatives, while they were moving through an electrophoretic solution containing OPA in the electric field, and the resultant OPA-amino acids were concurrently analyzed by zone electrophoresis with UV detection. A deep trough appeared based on sample-reagent displacement, and the base 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-capillary technique is the simplest of all techniques of pre-capillary and in-capillary derivatizations, and there was good linearity between relative peak area and amino acid concentration. The quantification was reproducible with R.S.D.similar to 3.5%. The rate constant of the derivatization reaction could be roughly estimated by plotting logarithm of amino acid concentration vs. reaction time. The obtained values were approximately identical with the values obtained by the zone-passing technique. This paper also compares this technique with other techniques of in-capillary derivatization with respect to peak area, signal-to-noise ratio and column efficiency. (C) 1998 Elsevier Science EX All rights reserved.