Chromatography materials — For silica gel used as an HPLC/flash adsorbent, which pore diameters are most commonly selected for general separations?

Introduction / Context:
Pore size is a critical property of silica gel that affects surface area, mass transfer, and suitability for separating molecules of different sizes. In preparative chromatography and many analytical applications, standard pore sizes are used for robustness and broad applicability.

Given Data / Assumptions:

• Spherical/irregular silica gels are available in multiple pore sizes (measured in Å).
• General organic separations (small molecules) prefer mid-range pores for a good balance of surface area and flow.
• Very small or very large pores are specialty options.

Concept / Approach:
Silica with ~60 Å or ~100 Å pores is widely adopted for small-molecule separations because it offers high surface area without excessively slow diffusion. Larger pores (e.g., 300 Å) are used for peptides/proteins due to size-exclusion considerations, not typical small-molecule work.

Step-by-Step Solution:

Verification / Alternative check:
Manufacturer datasheets and methods frequently recommend 60 Å or 100 Å silica for routine reversed-phase bonding (after derivatization) or normal-phase adsorption columns.

Why Other Options Are Wrong:

• 10 and 50 Å: too small for many applications; less common for general work.
• 100 and 150 Å: 150 Å skews toward larger molecules; not the most common pair.
• 150 and 200 Å: typically for large biomolecules.
• 20 and 30 Å: uncommon for standard workflows.

Common Pitfalls:
Assuming larger pores are always better; they reduce surface area and change retention, which can harm resolution for small molecules.

Final Answer:
60 and 100 Å