Supercritical fluid chromatography is not (only) normal-phase chromatography

Area of Science:

• Analytical Chemistry
• Chromatography

Background:

• Supercritical fluid chromatography (SFC) has been established for over 60 years.
• Carbon dioxide is a primary mobile phase component in modern SFC.
• Misconceptions persist regarding SFC's classification and capabilities.

Purpose of the Study:

• To critically evaluate the criteria used to categorize SFC as a normal-phase chromatographic technique.
• To reassess the historical and current understanding of SFC based on its fundamental principles.
• To challenge the narrow
• normal-phase

Main Methods:

• Review of historical development and foundational knowledge of SFC.
• Analysis of factors influencing SFC retention mechanisms, including stationary phase polarity, analyte elution order, mobile phase properties, and retention behavior.
• Examination of adsorption mechanisms in SFC.

Main Results:

• SFC exhibits characteristics that align with normal-phase chromatography under specific conditions.
• However, these characteristics are not universally applicable, and SFC can deviate significantly from normal-phase behavior.
• The classification of SFC as strictly normal-phase is an oversimplification that overlooks its broader applicability.

Conclusions:

• The categorization of SFC as solely a normal-phase technique is a limiting perspective.
• A comprehensive understanding of SFC requires acknowledging its complex retention mechanisms and diverse capabilities.
• Moving beyond the "normal-phase" label is crucial for fully realizing SFC's potential in analytical separations.