Better Retention for Polar Analytes and Versatility with TYPE‑C™ Silica‑Hydride 

1) Introduction

In classic reversed‑phase HPLC, column manufacturers often end‑cap residual silanol groups on silica to suppress secondary interactions and produce a more uniformly hydrophobic surface. This treatment generally improves peak shape and reproducibility for neutral or non‑polar, hydrophobic analytes. However, it can compromise retention and selectivity for polar compounds.

Understanding when to use non‑end‑capped columns—and how modern TYPE‑C™ silica‑hydride columns remove the need for end‑capping—can materially improve method performance and development agility. 

2) End‑Capping in Traditional RP: Purpose and Benefits

End‑capping reacts remaining Si–OH groups with small silyl reagents to dampen silanol activity. The result is a surface that:

• Minimizes tailing and undesired secondary interactions,
• Delivers more consistent retention, and
• Performs exceptionally well for hydrophobic or neutral analytes in conventional reversed‑phase mode.

These attributes explain why end‑capped phases are often the default starting point in routine reversed‑phase assays. 

3) Where End‑Capping Falls Short: Polar Analytes

Because end‑capping renders the surface more uniformly hydrophobic, many polar molecules exhibit:

• Insufficient retention (early elution),
• Compressed selectivity, and
• Difficulty resolving closely related polar species.

In such cases, analysts may deliberately choose non‑end‑capped columns to regain polar interactions at the surface and enhance retention and resolution.

4) Why Use a Non‑End‑Capped Column?

Non‑end‑capped stationary phases maintain accessible silanol (polar) sites, which can:

• Increase retention for highly polar and ionizable compounds,
• Produce alternative selectivity vs. fully end‑capped C18 phases, and
• Enable successful separations when standard RP methods fail.

Trade‑offs may include more pronounced surface activity and, with traditional silica, potentially greater variability in mixed matrices. 

5) A Modern Alternative: Cogent TYPE‑C™ (Silica‑Hydride) Columns

TYPE‑C™ columns use a silica‑hydride surface rather than the typical silica‑hydroxyl surface. This chemistry provides a unique balance that does not require end‑capping yet supports strong retention of both polar and non‑polar analytes.

Crucially, TYPE‑C enables operation in Reversed‑Phase (RP) and Aqueous Normal Phase (ANP) on the same column, expanding your method toolbox without changing hardware. 

5.1 Key Advantages

• No end‑capping required while still achieving clean peak shapes.
• Dual‑mode capability (RP + ANP) for broad analyte polarity ranges.
• Retention of polar analytes that under‑retain on fully end‑capped RP columns. 

6) Practical Selection Guide

7) Conclusions

• End‑capped RP columns remain best for hydrophobic/neutral compounds where reduced silanol activity ensures predictable behavior. 
• Non‑end‑capped columns are a strategic choice when polar analytes elute too early or lack selectivity on fully end‑capped phases.
• Cogent TYPE‑C™ silica‑hydride technology provides a no‑end‑capping alternative that effectively retains both polar and non‑polar analytes and supports RP and ANP modes, simplifying method development across diverse matrices.