Unique Selectivity of a Four Component Mixture Using Tris-(3,5-dimethylphenyl) Carbamoyl Amylose Chiral Stationary Phases (CSPs) Under Normal Phase and SFC Conditions

The Application Notebook

The Application Notebook, The Application Notebook-06-01-2013, Volume 0, Issue 0

Regis Technologies, Inc.

Chiral separations of multicomponent mixtures of enantiomers and diastereomers are often difficult to resolve by a single isocratic method. The inherent variability in chemically equivalent CSPs can contribute as a factor in developing a suitable LC or SFC method and resolve the individual isomers.

A proprietary compound mixture recently screened consisted of two diastereomers and their respective enantiomers. We desired to develop analytical and preparative methods under SFC mobile phase. Upon initial screening, distinct differences between two chemically equivalent CSPs, RegisPack and a clone, were noted.

Under normal phase LC conditions the multicomponent mixture resolved well under CSP clone but not as well using RegisPack® (Figures 1 and 2).

Figure 1 (top): Sample: proprietary. Column: CSP Clone, 25 cm × 4.6 mm, 5 μm. Mobile phase: hexanes/ethanol/methanol 92:4:4. Flow rate: 1.5 mL/min. Figure 2 (bottom): Sample: proprietary. Column RegisPack, 25 cm × 4.6 mm, 5 μm. Mobile phase: hexanes/ethanol/methanol 92:4:4. Flow rate: 1.5 mL/min.

Both CSPs were also evaluated under SFC for both analytical method development and preparative for isomer isolation. Peak resolution was diminished for an isomer pair under the CSP clone and not suitable for SFC analytical or preparative work (Figure 3). However, the RegisPack resolution was noticeably enhanced and used for an SFC analytical method and a preparative separation (Figure 4).

Figure 3 (top): Sample: proprietary. Column: CSP Clone 25 cm × 4.6 mm, 5 μm. Mobile phase: CO2/methanol 80:20. Flow rate: 4.0 mL/min. Figure 4 (bottom): Sample: proprietary. Column: RegisPack 25 cm × 4.6 mm, 5 μm. Mobile phase: CO2/methanol 80:20. Flow rate: 4.0 mL/min.

Conclusion

Differences in silica, the coating process, and packing are variables in the performances of chemically equivalent chiral stationary phases. The differences tend to be negligible in most circumstances. However, compound specific applications consisting of complex or multicomponent mixtures can be profoundly influenced by these differences and, thus, requires a direct comparison per separation project.

Regis Technologies, Inc.

8210 Austin Ave., Morton Grove, IL 60053

tel. (847) 583-7661, fax (847) 967-1214

Website: www.registech.com/chiral