Investigation into the performance and stability of immobilized and coated polysaccharide columns in supercritical fluid chromatography

In this study, the performance of the widely used “golden four” coated chiral stationary phases (Chiralpak AD-3, Chiralcel OD-3, Chiralpak AS-3, and Chiralcel OJ-3) was compared with their corresponding immobilized versions (Chiralpak IA-3, Chiralpak IB-3, Chiralpak IB N-3, Chiralpak IH-3, and Chiralpak IJ-3) under supercritical fluid chromatography (SFC) conditions with a set of 30 racemic compounds. Using the traditional modifiers, methanol and isopropanol, the immobilized columns (Chiralpak IB N-3 and Chiralpak IH-3) showed an improved general ability to successfully resolve the enantiomers of the target analytes relative to their coated versions (Chiralcel OD-3 and Chiralpak AS-3), while the coated columns (Chiralpak AD-3, Chiralcel OD-3, and Chiralcel OJ-3) performed better than their immobilized versions (Chiralpak IA-3, Chiralpak IB-3, and Chiralpak IJ-3). An investigation of the non-traditional modifiers, dichloromethane, ethyl acetate, and tetrahydrofuran with immobilized columns, revealed a generally decreased ability to successfully resolve the enantiomers of the target analytes, relative to the use of the traditional modifiers, methanol and isopropanol. The stability of the coated columns (Chiralpak AD-H and Chiralcel OD-H) was evaluated by injecting “forbidden” solvents, including dichloromethane, dimethyl sulfoxide, and tetrahydrofuran. After 200 injections of these solvents on coated columns, the retention factors and resolutions slightly decreased, and a significant increase in column backpressure was observed, indicating some degree of stationary phase degradation.