What Is the Purpose of Different Bonded Phases on Cogent TYPE‑C™ Silica?

On Cogent TYPE‑C™ silica‑hydride columns, the bonded phase you choose (e.g., C18, Cholesterol, C8, C3, Phenyl, Diol, Undecanoic Acid, etc.) directly shapes how the column behaves in Reversed‑Phase (RP) and Aqueous Normal Phase (ANP) modes.

In general, with little or no surface modification, ANP retention is stronger than RP under the same method conditions; as the bonded group size, surface coverage, and carbon load increase, the column expresses more pronounced RP behavior. 

How to use this in method development

• If your target analytes are polar/ionizable and you want ANP selectivity, start with minimally modified TYPE‑C™ phases (e.g., silica‑hydride or lightly bonded chemistries) and a high‑organic/low‑water gradient typical for ANP. Expect stronger ANP retention in this regime. 
• If you need classic RP behavior (hydrophobic interaction, water‑rich elution increasing retention), select more heavily bonded phases (e.g., C18, Cholesterol) where higher carbon load and surface coverage shift the mechanism toward RP.

Practical implications

• Selectivity tuning: Switching from a lightly bonded TYPE‑C™ phase to a higher‑carbon‑load phase can increase hydrophobic interactions and alter elution order in mixed analyte sets. 
• Mechanism steering: Keeping method conditions constant, your bonded phase choice is a direct lever to emphasize ANP (light/none) vs RP (heavier) behavior. 
• Column family consistency: Because these are all TYPE‑C™ surfaces, you can explore RP ↔ ANP selectivity within the same column family, minimizing re‑validation effort. (See CRC entries on ANP setup for deeper background.) 

Rule of thumb: Less bonding → more ANP‑dominant behavior; more/larger bonding and higher carbon load → more RP‑dominant behavior.