Silica‑Based | Ionized Above pH 5 | Designed to Retain Acids
Cogent IEX WAX™ HPLC columns are weak anion exchange (WAX) columns designed for the separation and purification of acidic and negatively charged compounds in USP® L9 ion exchange methods and routine analytical applications. These silica‑based columns provide pH‑dependent ionization, allowing analysts to fine‑tune retention and selectivity by adjusting mobile phase conditions.
Ion exchange chromatography is one of the most widely used techniques for separating charged, polar molecules, and Cogent IEX WAX™ columns offer controlled, flexible anion exchange behavior for methods where variable ionization is advantageous.
How Ion Exchange Chromatography Works
Ion exchange (IEX) chromatography separates charged analytes through reversible electrostatic interactions with ionic functional groups bonded to the silica surface. Common analytes include:
Organic acids
Amino acids
Proteins and peptides
Other polar or ionic compounds
Retention occurs via the exchange of ions between analytes in the mobile phase and oppositely charged ligands on the stationary phase. Selectivity and retention are influenced by mobile phase pH and ionic strength.
The functional pH range for Cogent IEX WAX™ columns is 5 to 8.
Weak Anion Exchange (WAX) Selectivity
Anion exchange columns contain positively charged functional groups that retain negatively charged (acidic) analytes.
Cogent IEX WAX™ columns use diethylaminopropyl (DEAE) functional groups, which become ionized only within a specific pH range. Above approximately pH 5, the functional group carries a positive charge and participates in anion exchange interactions.
This pH‑dependent behavior provides additional selectivity control compared to strong anion exchange columns.
What “Weak” Ion Exchange Means
The term “weak” ion exchange does not refer to weaker analyte binding. Instead, it describes the pH‑dependent ionization of the functional group:
Weak anion exchange (WAX): Functional groups are ionized only within a defined pH range and lose charge outside that range.
This allows analysts to modulate retention by adjusting mobile phase pH, making weak exchangers particularly useful for method development and fine selectivity control.
Column Construction and Specifications
Cogent IEX WAX™ HPLC columns are manufactured with:
Diethylaminopropyl (DEAE) functional groups
Bonded to Cogent RP™ world‑class, high‑purity silica
5 µm or 10 µm particle sizes
100 Å pore size
Functional pH range: 5–8
This design supports reproducible performance in both regulated and non‑regulated laboratory environments.
Key Features and Benefits
Designed for USP® L9 ion exchange methods
Weak anion exchange (WAX) chemistry
Retains acidic and negatively charged compounds
pH‑dependent ionization for selectivity control
Silica‑based stationary phase
Predictable, tunable retention behavior
Available in 5 µm and 10 µm particle sizes
Typical Applications
Organic acids
Acidic pharmaceuticals
Amino acids
Peptides and proteins
USP® ion exchange methods
Polar compound purification
Additional Resources
Learn more about Cogent IEX™ 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
