The analysis of pharmaceutical bases on a silica stationary phase by capillary electrochromatography using aqueous mobile phases

Abstract

The capillary electrochromatographic (CEC) separation of a range of pharmaceutical bases was investigated on a commercially available silica stationary phase using aqueous mobile phases. The effects of mobile phase composition, buffer pH, applied voltage, and buffer anion on the retention behaviour of these bases were studied. Promising chromatography was obtained at pH 7.8 but was later found to be irreproducible. However, successful and reproducible chromatography of the bases was achieved at pH 2.3. We have previously demonstrated that the addition of mobile phase additives such as TEA-phosphate at low pH values has resulted in excellent CEC analysis of bases on reversed-phase packing materials. The same approach was applied to the analysis of bases on the silica phase in order to improve peak shape. Excellent chromatography was obtained for the analysis of strong pharmaceutical bases such as benzylamine, nortriptyline and diphenhydramine. The experimental investigations have shown that the CEC separation of a range of pharmaceutical bases can routinely be achieved with excellent peak shapes and peak efficiencies as high as 320,000 plates m 1.

Optimized preparation of poly(styrene‐co‐ divinylbenzene‐co‐methacrylic acid) monolithic capillary column for capillary electrochromatography

“…Some approaches have now been undertaken to overcome these problems [29,[44][45][46][47]. In order to improve the peak symmetry of basic compounds, a conventional method would be to add a competing base to the mobile phase to compete with the analytes [44][45][46]. This was expected to result in efficient separations with improved peak shapes.…”

Polar stationary phases for capillary electrochromatography

“…Gillott et al [26] also used a bare silica column for the separation of basic compounds by adding amines into the mobile phase to reduce peak tailing. Comparing triethanolamine (TEOA) and triethylamine (TEA) as additives, they found TEOA had the more desirable effects on separation to improve peak symmetry, while a high EOF was still maintained for its lesser degree of masking for silanol groups on the inner surface.…”

A Critical Appraisal of Capillary Electrochromatography

“…Nevertheless, CEC capillaries packed with bare silica particles can be efficient and selective for analyzing many basic types of analytes (20). However, when it comes to analyzing peptides and proteins, reversed-phase or mixed-mode sorbent systems are the preferred options.…”