Triamine-bonded stationary phase for open tubular capillary electrochromatography

A multi-functional separation column modified with 3-[2-(2-aminoethylamino)ethylamino] propyl-trimethoxysilane was developed for open tubular capillary electrochromatography. This functional hydrophilic triamine-bonded open tubular column could generate both anodic and cathodic EOF. When the pH of the running buffer was below 5.3 (30% 3-[2-(2-aminoethylamino)ethylamino] propyl-trimethoxysilane, v/v), the anodic EOF was exhibited, which greatly prevented the undesired adsorptions of basic proteins on the capillary inner wall. Favorable separation of four basic proteins (viz. trypsin, ribonuclease A, lysozyme and cytochrome c) was successfully achieved at pH 3.5 of 10  mmol/L phosphate buffer. The column efficiencies of proteins were in the range from 87,000 to 110,000  plates/m, and the RSD values for migration time of four proteins were less than 1.2% (run-to-run, n=5). The ionic analytes were also separated efficiently in the co-electroosmotic mode. The average efficiencies ranged from 81,000 to 190,000  plates/m for seven aromatic acids and 186,000-245,000  plates/m for four nucleoside monophosphates, respectively, and good capillary column repeatability was gained with RSD of the migration time not more than 3.0%. The triamine-bonded open tubular capillary column is favorable to be an alternative functional medium for the further analysis of basic proteins and anionic analytes.