Evaluation of an amide‐based stationary phase for supercritical fluid chromatography

Abstract

A relatively new stationary phase containing a polar group embedded in a hydrophobic backbone (i.e., ACE® C18-amide) was evaluated for use in supercritical fluid chromatography. The amide-based column was compared with columns packed with bare silica, C18 silica, and a terminal-amide silica phase. The system was held at supercritical pressure and temperature with a mobile phase composition of CO2 and methanol as cosolvent. The linear solvation energy relationship model was used to evaluate the behavior of these stationary phases, relating the retention factor of selected probes to specific chromatographic interactions. A five-component test mixture, consisting of a group of drug-like molecules was separated isocratically. The results show that the C18-amide stationary phase provided a combination of interactions contributing to the retention of the probe compounds. The hydrophobic interactions are favorable; however, the electron donating ability of the embedded amide group shows a large positive interaction. Under the chromatographic conditions used, the C18-amide column was able to provide baseline resolution of all the drug-like probe compounds in a text mixture, while the other columns tested did not.

Separation of diarylethene‐based photoswitchable isomeric compounds by high‐performance liquid chromatography and supercritical fluid chromatography

“…Comparisons between the two techniques for the separation of a wide range of compounds and applications are readily available in the literature [16][17][18][19][20][21]. This technique provides a normal-phase type of separation mode, mainly using supercritical CO 2 as the mobile phase which can contain low quantities of an organic co-solvent (e.g., methanol), used as a modifier to tune the selectivity of the separation [22][23][24][25]. Supercritical CO 2 is less viscous and has higher diffusivity than the mobile phases commonly employed in HPLC, leading to higher flow rates than in HPLC, corresponding to faster analysis times [26].…”