Ascentis RP-Amide HPLC Columns

Ultra-Low Bleed Alkyl Amide Phase that Rivals C18 as a Generic Scouting Column. Excellent Peak Shape and Resolution, Especially for Polar Compounds or Mixtures of Compound Polarity.

As pioneers in embedded polar group (EPG) phases for HPLC, Supelco is pleased to offer Ascentis RP-Amide, which has all the benefits of enhanced polar compound retention and selectivity, without any of the disadvantages of competitive EPG phases.


  • Improved peak shape for bases compared to C18
  • Different selectivity than C18 or C8
  • for wide range of polar compounds (especially acids)
  • Lower bleed than competitive EPG phases
  • 100% aqueous compatible

Structure of Ascentis RP-Amide

USP Code: L60
Bonded Phase Description: Stable amide group embedded in an 18-carbon chain
Endcapped: Yes
Particle composition: Type B silica gel
Particle Purity: <5 ppm metals
Particle Shape: Spherical
Particle Size: 3, 5 and 10 µm
Pore Size: 100 Å
Surface Area: 450 m2/g
Carbon Load: 19.5 %
pH Range (recommended): 2 to 8
Extended pH range*: 1.5 to 10

Key Applications

Small, water soluble molecules and peptides, H-bond donors, acids, phenols, basic compounds, polar compounds

Ordering Information for Ascentis RP-Amide HPLC columns


Ascentis RP-Amide can be used for many of the same separations as a C18 while avoiding some of the disadvantages of C18 such as poor wettability in high aqueous mobile phases. In addition, it is much more retentive for those molecules that can interact by hydrophobic interactions and also by H-bonding with the amide group. Compared to alkylonly phases, Ascentis RP-Amide has enhanced retention and selectivity for phenols, organic acids and other polar solutes due to strong H-bonding between the amide carbonyl (H-bond acceptor) and H-bond donors, like phenols and acids. Compared to other EPG phases, like carbamates, ureas, sulfonamides and ethers, Ascentis RP-Amide gives retention comparable to C18 and C8 for easy column comparison without the need to change mobile phase conditions.

LC-MS Implications

Unlike other amide-based phases, Ascentis RP-Amide uses an amidosilane reagent and a one-step bonding method similar to C18. Polymeric reagents are also employed to achieve maximum stability and low bleed with all modern HPLC detectors.


  • Generally, acids are retained more and bases retained less on RP-Amide compared to C18 and C8 columns.
  • Methanol can be comparable in elution strength to acetonitrile when compounds are retained by H-bonding mechanism on the RP-Amide phase.

* Under certain conditions, the Ascentis family can be operated in the extended pH range. For more details, see “Acid/Base Stability of Silica Based on C8, C18, and Amide HPLC Columns” (T406018 - 530Kb pdf)