Chromatographic silanol activity test procedures: the quest for a universal test.

Area of Science:

• Analytical Chemistry
• Chromatography
• Materials Science

Background:

• Reversed-phase chromatography (RPC) is a dominant liquid chromatography technique.
• Microparticulate silica is the predominant support for RPC stationary phases due to its favorable properties.
• Silica surface silanol groups significantly influence RPC performance but their exact role remains debated.

Purpose of the Study:

• To review the surface chemistry of silica, focusing on silanol groups.
• To critically examine various proposed methods for testing silanol activity in RPC stationary phases.
• To compare different silanol activity testing methods and highlight discrepancies.

Main Methods:

• Review of existing literature on silica surface chemistry and derivatization.
• Focus on chromatographic probe molecules to assess silanol interactions.
• Comparison of various proposed silanol activity tests.

Main Results:

• Different types of silanols (isolated, vicinal, geminal) exhibit unique properties affecting chromatography.
• The distribution of silanol types, not just their total number, impacts stationary phase characteristics.
• Current methods for measuring silanol accessibility and interaction show inconsistent results across different tests.

Conclusions:

• There is no universally agreed-upon method for quantifying silanol activity in silica-based RPC columns.
• Further research is needed to establish standardized and reliable methods for silanol activity assessment.
• Understanding and controlling silanol activity is critical for developing improved RPC stationary phases.