Overview
Cogent™ TYPE-C™ columns are designed to operate in multiple chromatographic modes, including Reversed Phase (RP), HILIC, and Organic Normal Phase (NP). Because these columns may be used with significantly different solvent systems, proper storage and conditioning procedures are important to maintain column performance and avoid solvent incompatibility problems.
Selecting the correct storage solvent based on the column's next intended use can simplify startup procedures and reduce equilibration times.
Recommended Storage Solvents
For Reversed Phase and HILIC Applications
When the column will next be used in either Reversed Phase or HILIC mode, the recommended storage solvent is:
100% Acetonitrile
Benefits include:
- Maintains a wetted stationary phase
- Supports rapid startup
- Compatible with many RP and HILIC methods
- Reduces conditioning requirements prior to use
For Organic Normal Phase Applications
When the column will next be used in Organic Normal Phase mode, the recommended storage solvent is:
100% Hexane
or another suitable non-polar Normal Phase solvent.
When storing columns for NP use:
- Cap both ends securely.
- Label the storage solvent.
- Identify the column as prepared for NP operation.
General Storage Requirements
The following recommendations apply to all Cogent™ TYPE-C™ columns regardless of chromatographic mode:
Store at Room Temperature
Columns should be stored under normal laboratory room-temperature conditions.
Avoid:
- Refrigeration
- Freezing
- Excessive heat
Never Allow the Column to Dry
Columns should always contain an appropriate storage solvent.
Before storing:
- Flush the column with the recommended storage solvent.
- Install end plugs securely.
- Ensure the column remains filled with solvent.
Drying may adversely affect chromatographic performance and increase conditioning time.
Avoid Long-Term Water Storage
Columns should not be stored in pure deionized water.
Potential concerns include:
- Microbial growth
- Changes to system cleanliness
- Increased startup preparation requirements
When aqueous storage is unavoidable, follow validated laboratory procedures.
Overnight Storage Procedures
Reversed Phase and HILIC Methods
For overnight storage:
- Flush the column using approximately 8 to 10 column volumes of acetonitrile.
- Install end plugs.
- Store at room temperature.
Normal Phase Methods
For overnight storage:
- Flush the column using approximately 8 to 10 column volumes of hexane or the non-polar solvent currently being used.
- Install end plugs.
- Store at room temperature.
Long-Term Storage Procedures
Reversed Phase and HILIC Applications
For extended storage:
- Flush the column with approximately 15 to 20 column volumes of acetonitrile.
- Install end plugs.
- Return the column to its storage container.
- Store at room temperature.
Normal Phase Applications
For extended storage:
- Flush the column with approximately 15 to 20 column volumes of hexane.
- Install end plugs.
- Label the storage solvent used.
- Return the column to its storage container.
- Store at room temperature.
Switching Between Chromatographic Modes
Proper solvent transitions are important because HILIC, Reversed Phase, and Normal Phase methods often use solvent systems that are not directly compatible.
Using intermediate solvents helps prevent:
- Solvent precipitation
- Frit blockage
- Excessive backpressure
- Baseline instability
Transitioning from Reversed Phase or HILIC to Normal Phase
Recommended sequence:
- Flush with 100% methanol.
- Flush with 100% methylene chloride.
- Equilibrate with the desired Normal Phase mobile phase.
This sequence helps establish solvent compatibility before introducing non-polar mobile phases.
Transitioning from Normal Phase to Reversed Phase or HILIC
Recommended sequence:
- Flush with 100% methylene chloride.
- Flush with 100% methanol.
- Equilibrate in the desired Reversed Phase or HILIC mobile phase.
This approach helps prevent immiscible solvent interactions during mode changes.
Conditioning Before First Use
When placing a new column into service:
- Transition gradually from the shipping solvent to the initial mobile phase composition.
- Avoid sudden changes between incompatible solvents.
- Equilibrate the column with several column volumes of the starting mobile phase before injecting samples.
Proper conditioning promotes stable retention and reproducible chromatographic performance.
Routine Conditioning Between Sequences
When pausing work between analytical runs:
Reversed Phase and HILIC
- Flush with acetonitrile.
- Cap both ends.
- Store appropriately.
Normal Phase
- Flush with the intended non-polar solvent.
- Cap both ends.
- Store appropriately.
This helps prevent solvent evaporation, contamination, and salt deposition.
Troubleshooting After Storage
Elevated Backpressure
Possible causes include:
- Residual salts
- Incompatible solvent transitions
- Incomplete equilibration
Corrective action:
- Repeat the recommended solvent-transition procedure.
- Re-equilibrate using the intended mobile phase.
Retention Changes
Retention changes immediately after startup are often caused by:
- Incomplete equilibration
- Mobile phase composition differences
- Temperature variation
Additional equilibration may be required before normal performance is restored.
Baseline Instability
Following buffered methods:
- Ensure salts have been adequately removed before storage.
- Flush thoroughly with appropriate storage solvent.
- Allow sufficient equilibration before analysis.
Special Note for Diamond Hydride™ Columns
Diamond Hydride™ columns utilize a dedicated storage procedure that differs from other TYPE-C™ phases.
Always follow the specific Diamond Hydride™ storage and conditioning recommendations before long-term storage or chromatographic mode changes.
Key Takeaways
- Store Reversed Phase and HILIC columns in 100% acetonitrile.
- Store Normal Phase columns in an appropriate non-polar solvent such as hexane.
- Never allow columns to dry out.
- Use proper intermediate solvents when changing chromatographic modes.
- Flush columns before overnight and long-term storage.
- TYPE-C™ columns typically equilibrate more rapidly than conventional silica columns.
- Diamond Hydride™ columns require a separate storage protocol.
Additional Resources
For phase-specific care instructions, conditioning procedures, solvent compatibility guidance, and maintenance recommendations, view:
Diamond Hydride™ Column Storage Procedures, Conditioning Methods, and Maintenance Resources
** Diamond Hydride™ columns have a special storage protocol, given click HERE.
