Silica‑Based IEX Columns | USP® L9 Class | Designed for Polar and Charged Compounds
Cogent Ion Exchange (IEX) HPLC columns are silica‑based stationary phases designed for the separation, analysis, and purification of charged (polar) molecules in USP® L9 class methods and routine laboratory applications. Ion exchange chromatography remains one of the most widely used techniques for separating ionic compounds based on their charge interactions with functional groups bonded to the silica surface.
The Cogent IEX portfolio includes strong and weak anion and cation exchange columns, providing method flexibility across a wide pH range and analyte classes.
What Is Ion Exchange Chromatography (IEX)?
Ion exchange chromatography (IEX) is a powerful HPLC technique used to separate charged molecules such as:
Amino acids
Proteins and peptides
Organic acids and bases
Other polar and ionic compounds
Retention is based on the reversible exchange of ions between the analyte in the mobile phase and oppositely charged functional groups bonded to the column’s silica surface. Retention can be controlled by adjusting pH, ionic strength, and mobile phase composition.
As a general guideline:
Use acids in basic mobile phases
Use bases in acidic mobile phases
Cation vs Anion Exchange Columns
Cation Exchange Columns
Cation exchange columns contain negatively charged functional groups that retain positively charged analytes. These columns are typically used to retain and separate basic compounds.
Anion Exchange Columns
Anion exchange columns contain positively charged functional groups that retain negatively charged analytes. These columns are commonly used to retain and separate acidic compounds.
Understanding Strong vs Weak Ion Exchange
The terms “strong” and “weak” ion exchange do not refer to the strength of analyte binding. Instead, they describe how the ionization state of the functional group changes with mobile phase pH:
Strong Ion Exchange (SAX / SCX): Functional groups remain ionized across the full usable pH range.
Weak Ion Exchange (WAX / WCX): Functional groups are ionized only within a specific pH range.
This distinction allows analysts to fine‑tune selectivity and retention by adjusting pH conditions.
Cogent Ion Exchange HPLC Column Options
Cogent IEX SAX™ — Strong Anion Exchange Columns
Quaternary amine functional groups
Retains acidic (negatively charged) compounds
Bonded to Cogent RP™ high‑purity silica
Particle sizes: 5 µm or 10 µm
Pore size: 100 Å
Functional pH range: 2.5–8
Cogent IEX SCX™ — Strong Cation Exchange Columns
Sulfonic acid functional groups
Retains basic (positively charged) compounds
Bonded to Cogent RP™ high‑purity silica
Particle sizes: 5 µm or 10 µm
Pore size: 100 Å
Functional pH range: 2.5–8
Cogent IEX WAX™ — Weak Anion Exchange
Diethylaminopropyl functional groups
Retains acidic compounds
Bonded to Cogent RP™ high‑purity silica
Particle sizes: 5 µm or 10 µm
Pore size: 100 Å
Functional pH range: 5–8
Cogent IEX WCX™ — Weak Cation Exchange
Carboxylic acid functional groups
Retains basic compounds
Bonded to Cogent RP™ high‑purity silica
Particle sizes: 5 µm or 10 µm
Pore size: 100 Å
Functional pH range: 2.5–7
Key Features and Benefits
Designed for USP® L9 ion exchange methods
Silica‑based stationary phases
Strong and weak anion and cation exchange options
Suitable for polar and charged analytes
Reliable retention and reproducibility
Compatible with routine and regulated workflows
Multiple particle size options
Typical Applications
USP® ion exchange methods
Amino acids and peptides
Proteins and biomolecules
Organic acids and bases
Pharmaceutical and bioanalytical separations
Additional Resources
Learn more about Cogent ion exchange HPLC columns
Column Protection Recommendation
Important: MICROSOLV technical support strongly recommends using the Cogent Column Filter, which is included with each column, whenever possible. Column filters help protect against particulates, extend column lifetime, and maintain consistent chromatographic performance.
👉Learn more about the Cogent Column Filter for HPLC column protection
