Effects of aliphatic amines on capillary electrochromatographic performance of tricyclic antidepressants on octadecylsilica

Adding aliphatic amines to the mobile phase improves peak symmetry and efficiency in capillary electrochromatography of tricyclic antidepressants on octadecylsilica. The most hydrophobic aliphatic amine studied, dimethyloctylamine (DMOA), was the most efficient. Despite the fact that the amine additives substantially reduced the electroosmotic flow, the retention of the analytes decreased indicating a strong competitive effect of the additives. DMOA gave the largest retention decrease, and simultaneously reduced the resolution, indicating that silanophilic interaction is significant to the separation. Highest efficiencies were obtained at the lowest pH (2.8). Acetonitrile influenced both efficiency and peak symmetry, and best results were obtained at 60%.