Separation of catecholamines with capillary electrophoresis by using some static and dynamic coatings in capillaries

The study was undertaken to improve the separation and the concentration sensitivity of catecholamines by capillary electrophoresis (CE) using laboratory‐coated capillaries. The coatings were made by adsorption using in‐run modification and by covalent bonding. The coating solutions used in‐run contained triethylamine (TEA), glycine or morpholine in acetate (pH 4.0) or phosphate buffers (pH 3.0). In the covalent bonding technique the coating was made with MAPT ((γ‐metacryloxypropyl)‐trimethoxysilane) using 1, 10, 20, 30, 40, and 50% solutions. The results obtained with the capillaries indicated that coating improved the efficiency of the CE systems in separation of the cationic catecholamines in ammonium acetate and sodium phosphate solutions. Furthermore, the analyses were more reproducible than if they were performed in bare silica capillaries. The highest plate numbers were obtained with the 1% and 50%‐MAPT coated capillaries or with 50 mM ammonium acetate–40 mM TEA electrolyte solution, although 20% and 30% MAPT‐coated capillaries gave the best resolution for the analytes.