Using subcritical/supercritical fluid chromatography to separate acidic, basic, and neutral compounds over an ionic...

Area of Science:

• Analytical Chemistry
• Chromatography
• Separation Science

Background:

• Supercritical fluid chromatography (SFC) is a powerful separation technique.
• Developing versatile stationary phases is crucial for simultaneous separation of diverse compound classes.
• Ionic liquids offer unique properties for chromatographic applications.

Purpose of the Study:

• To develop and evaluate an ionic liquid-functionalized stationary phase for simultaneous SFC separation.
• To investigate the influence of operational parameters (pressure, temperature, co-solvents, additives) on separation.
• To demonstrate the separation of acidic, basic, and neutral compounds.

Main Methods:

• A novel stationary phase was prepared by covalently bonding 1-octyl-3-propylimidazolium chloride (an ionic liquid) to silica gel.
• The functionalized phase was packed into a 3.2mmx250mm column for SFC.
• Model compounds including acetaminophen, metoprolol, fenoprofen, ibuprofen, naphthalene, and testosterone were used to test the separation.

Main Results:

• Simultaneous separation of acidic, basic, and neutral compounds was achieved.
• Optimal separation conditions were identified as 20% MeOH co-solvent, 110 bar pressure, and 35°C column temperature.
• Hydrogen-bonding and hydrophobic interactions were identified as key mechanisms in the separation process.

Conclusions:

• The developed ionic liquid-functionalized stationary phase enables efficient simultaneous separation of diverse compounds by SFC.
• The method demonstrates good reproducibility with relative standard deviations for retention times and peak areas below 4% and 8%, respectively.
• This approach offers a promising alternative for complex mixture analysis in various scientific fields.