A Novel Covalently Bonded Amino-Silica for Capillary Ion Chromatography

Abstract

Capillary columns are at the core of chromatographic separation techniques. These columns were first invented for gas chromatography (GC), but due to the majority of the target compounds being neither volatile nor stable to be separated on a GC system using glass beads packed columns was adopted for LC (liquid chromatography). Packed capillary columns are made by packing a slurry of silica material under pressure with particles <15μm in diameter. Packed capillary columns for ion exchange chromatography (IEC) invented by Small and his coworkers is probably the most frequently used chromatographic media for identification and separation of ionic samples mainly; inorganic anions and cations, peptides and carbohydrates. The purpose of this study was to investigate the retention of anions on a chemically bonded 4-amino butyric acid onto the surface of silica gel. The stationary phase was effectively synthesized and packed. Selection of a suitable cation contained in the eluent resulted in retention and separation of anions and thus, it worked as the anion-exchange stationary phase. The tested anions’ elution order was iodate, bromate, bromide, nitrate, iodide and thiocyanate ions, with relatively sharp peaks, which is a common observation in ion exchange chromatography. It was observed that the analyte anion retention decreased with the increase in eluent concentration. Run-to-run repeatability of these anions under isocratic mode were analyzed on the prepared column, and the RSD value, n=5 of < 2% calculated over five or six consecutive runs when 40 mM, 60 mM and 80 mM solutions were used as the eluent. The effect of pH on the column’s inorganic anions retention was also explored. The anions were retained more in the column under acidic condition, and less under neutral conditions. The prepared column contained both bromide and nitrate inorganic anions.