On-column derivatization and analysis of amino acids, peptides, and alkylamines by anhydrides using capillary electrophoresis

This work demonstrates the use of an in-capillary procedure for derivatizat ion of amino acids, peptides, and alkylamines by anhydrides using capillary electrophoresis (CE). Migrating in an uncoated fused-silica capillary, plu gs of substrate and anhydride are injected separately and electrophoresed. Differential transport velocities permit the separate zones to penetrate ea ch other under an applied field, thereby facilitating reaction. In initial experiments the extent of reaction between tryptophan and acetic anhydride was examined and product amounts quantitated by CE. In separate experiments a series of amino acids and peptides were injected into the capillary and reacted with phthalic anhydride on-column to yield the phthalic derivatized species. Finally, on-column derivatization of alkylamines with phthalic an hydride was investigated and electrophoretic mobility related to molecular weight of the derivatized amines. These procedures illustrate the use of th e capillary as a microreactor in the facile synthesis of derivatized molecu les and ease of quantitation of reaction products under conditions of elect rophoresis.