Phenylaminopropyl‐functionalized stationary phase for open‐tubular capillary electrochromatography of alkaloids and aromatic acids

Abstract

A multi-functional open-tubular (OT) column covalently modified with [3-(phenylamino)propyl]trimethoxysilane (PPTMS) via a single-step silanization reaction has been developed, and employed for alkaloids and aromatic acids analytes by CEC. Both anodic and cathodic EOF could be gained in the PPTMS-bonded column, and anodic EOF was exhibited when the pH of running buffer was less than 8.0. Using thiourea as the EOF marker, a satisfactory column stability was denoted, and the RSD values for migration time and peak area were gained at 0.5 and 3.7% (intra-day, n=5), 1.7 and 5.6% (inter-day, n=3), 3.9 and 5.8% (column-to- column, n=16 in four batches). With anodic EOF mode (pH=2.0 of 10 mmol/L phosphate buffer), favorable separations of cationic alkaloids (viz. uridine, adenosine, cytidine, adenine, cytosine) were successfully achieved with column efficiencies ranging from 95,000 to 187,000 plates/m, and the undesired adsorption on the inter-wall of capillary column could be avoided. Besides, six anionic aromatic acids could be also separated efficiently in the co-electroosmotic mode with anodic EOF. And high efficiencies ranged from 176,000 to 235,000 plates/m were gained with a good repeatability. PPTMS-bonded capillary column might be used as an alternative functional medium to physical coating capillary column for the analyses of aromatic organic acids and bases.