The Cogent Diol™ HPLC Column is a TYPE-C™ silica hydride stationary phase designed primarily for HILIC separations of polar compounds. The bonded diol functionality provides unique selectivity for polar analytes including amino acids, vitamins, metabolites, organic acids, sugars and other highly water-soluble compounds that are often difficult to retain using traditional reversed-phase chromatography.
This guide provides recommended startup procedures, HILIC method development strategies, storage instructions, and best practices to help achieve reproducible, high-efficiency separations.
Related Resources
Choosing the Appropriate Separation Mode
HILIC (Recommended)
The Cogent Diol phase is optimized for HILIC applications involving highly polar compounds.
Typical Applications
- Amino acids
- Polar metabolites
- Vitamins
- Organic acids
- Polar pharmaceuticals
- Water-soluble compounds
Example Compounds (structures shown below)
- Pyridoxine
- Thiamine
- Uric Acid
Increasing Retention in HILIC
To increase retention:
- Increase organic solvent content.
- Reduce aqueous content.
Reversed-Phase (Limited Use)
The Cogent Diol stationary phase contains a bonded diol functionality on a short hydrocarbon chain and exhibits limited hydrophobic retention.
For typical non-polar compounds, consider:
- Cogent Bidentate C18™
- Cogent Bidentate C8™
- Cogent Phenyl Hydride™
- Cogent UDC-Cholesterol™
Before Using the Column
Before installation:
- Purge all solvent lines of previous mobile phases.
- Purge the injector system.
- Verify all solvents are fresh and HPLC-grade.
- Degas solvents before use.
- Prepare fresh buffers daily.
Startup Instructions
Initial Conditioning
- Install the column using standard laboratory procedures.
- Confirm all fittings and tubing are properly connected.
- Prepare a 50:50 organic solvent/water mixture containing all intended mobile-phase additives.
- Equilibrate the column for approximately 30 minutes.
- Switch to the starting mobile-phase conditions and allow the system to stabilize.
Column Protection
- Use a guard column whenever possible.
- Use inline filters whenever possible.
- Replace protection devices routinely.
Related Resource
HILIC Method Development
General HILIC Guidelines
The Cogent Diol phase is designed for HILIC chromatography.
To Increase Retention
- Increase acetonitrile content.
- Decrease aqueous content.
For most applications, acetonitrile is the preferred organic solvent.
Polar Neutral Compounds
Only sufficiently polar neutral compounds are likely to exhibit meaningful retention.
Examples include:
- Vitamins
- Polar metabolites
- Hydroxyl-containing compounds
Recommended starting conditions:
- 50% aqueous
- 50% acetonitrile
Increase organic content as required.
Acidic Compounds
To maximize HILIC retention:
- Ensure the analyte is ionized.
Recommended starting buffer:
- 10 mM ammonium formate
- or
- 10 mM ammonium acetate
Recommended starting pH:
- Approximately 6.5
Simple Samples
Start with:
- 50% aqueous buffer
- 50% acetonitrile
Increase organic content to achieve desired retention.
Complex Samples
Recommended scouting gradient:
- 90% acetonitrile
- To 20% acetonitrile
- Over approximately 10 minutes
Optimize gradient profile as needed.
Basic Compounds
For basic analytes:
Recommended starting additives:
- 0.1% formic acid
- or
- 0.2% acetic acid
Both isocratic and gradient methods can be effective depending on analyte complexity.
Selecting the Organic Solvent
Preferred
- Acetonitrile
Secondary Options
In many HILIC methods, methanol does not provide sufficient retention for highly polar compounds.
For non-UV detection methods such as:
- LCMS
- Light scattering detection
- Electrochemical detection
Acetone may be considered as an alternative organic modifier.
Troubleshooting Common Problems
Most performance issues originate from:
- Inadequate equilibration
- Mobile-phase composition
- Buffer concentration
- Contaminated solvent lines
- Improper sample solvent
- Sample overload
- Column contamination
Related Resource
Storage Instructions
When analysis is complete:
- Flush the column with approximately 90:10 organic solvent/water.
- Allow all system pressure to return to zero.
- Disconnect and cap the column for storage.
Important
Never disconnect a column under pressure. Pressure shock can damage the stationary phase and hardware.
Related Resources
Best Practices Summary
- Use the Cogent Diol phase primarily for HILIC methods.
- Use HPLC-grade solvents only.
- Degas all solvents.
- Prepare buffers fresh daily.
- Allow sufficient equilibration time.
- Increase organic solvent to increase retention.
- Use acetonitrile whenever possible.
- Consider acetone for LCMS and non-UV applications.
- Use column filters and guard columns when appropriate.
- Store in approximately 90:10 organic/water solvent.