Dynamic Axial Compression Column Packing Guide
Proper methods and precautions for Sunpure packing material in DAC columns
Packing Capacity Determination
Proper calculation of packing material is essential for optimal column performance.
Selection of Appropriate Solvent for Slurrying
- Normal-phase silica gel packing material: Use isopropanol
- Reversed-phase C18 packing material: Typically use isopropanol or ethanol
The ratio of slurrying reagent to packing material is approximately 2mL/1g.
Slurrying Process
Select an appropriate container according to the calculated volume and add the weighed packing material into it.
- Gradually pour the slurrying reagent into the packing material while stirring (avoid pouring all the reagent at once)
- Stir for 10-20 minutes
- If conditions permit, simultaneously heat the slurry to 35-40°C during this process to enhance the slurrying
- Ensure uniform dispersion of the packing material in the solvent until mixed into a uniform suspension
- Sonicate the completed slurry for 5 minutes to remove any trapped air bubbles
Packing Procedure
Preparation
Wash the column tube with methanol, and then blow it dry with an air gun to ensure no water/solvent residue.
Initial Setup
Toggle the hydraulic cylinder lifting switch to "UP" and the gas supply valve to "OPEN", slowly adjust the pressure regulating valve to increase the pressure. The plunger rod rises slowly, raising the piston head to a distance of more than 20cm from the port of the column tube to facilitate the follow-up operations.
Pressure Adjustment
Adjust the pressure regulating valve to the minimum opening, and toggle the air supply switch to "OFF" and the hydraulic cylinder lifting switch to the "DOWN" position.
Adding Slurry
Use a threaded plug to block the lower end of the column tube, and quickly add the slurry into the column tube. Wash the slurry container with isopropanol and pour it into the column tube. Rinse the wall of the tube with isopropanol until there is no residual packing material on the wall.
Initial Compression
Toggle the gas supply valve to the "ON" position and adjust the pressure regulating valve to gradually increase the pressure, allowing the plunger rod to descend to the upper port of the column as quickly as possible.
Piston Alignment
When the piston head is close to the upper port of the column, slow down the descent speed. Use a wash bottle to drip a small amount of isopropanol (for lubrication) onto the edge of the piston head, which can assist the piston head to align with the column tube port. Then press it down into the tube.
Pressure Application
After the piston head enters the upper port of the column, adjust the air pressure regulating valve to maintain the air pressure at about 0.2MPa. When the wave body inside the column is observed to reflux along the pipeline of the column head, quickly turn off the gas supply valve (by setting the gas supply valve to "OFF") and quickly remove the threaded plug at the lower end of the column tube to plug the pipeline of the column head with it.
Final Compression
Reopen the gas supply valve and adjust the pressure regulating valve so that the piston rod continues to descend at a uniform speed. Ensure that the pressure gauge does not exceed 0.3MPa at this time. Under pressure, slurry flows out of the outlet at the lower end of the column, and when the liquid no longer flows out, the piston head will also stop. This process should be controlled within 40 seconds to 1 minute.
Stabilization
Subsequently, adjust the pressure regulating valve to set the actual column loading pressure within the appropriate range, and let it stand for 30 minutes to stabilize the system.
Flushing and Testing
After allowing the system to stand for 30 minutes, flush the system with the mobile phase (such as methanol, etc.), starting with a flow rate of 1/5 of the intended operating flow rate and gradually increasing to the intended operating flow rate. During this process, ensure that the pressure does not exceed the packing pressure. Once the pressure stabilizes, connect the detector and test the column efficiency using the mobile phase.
Internal Column Pressure Guidelines:
- For a column packed with 10µm C18 packing material: typically 6-8MPa
- For a column packed with 10µm silica gel packing material: typically 5-7MPa
Discharging Procedure
Pressure Release
Adjust the pressure regulating valve to the minimum opening, set the hydraulic cylinder lifting switch to the "UP" position, slowly adjust the pressure regulating valve, so that the piston head is no longer tightly pressed on the upper end of the packing, and then adjust the pressure to the minimum.
Packing Removal
Place a suitable container at the bottom of the column. Unscrew the column base bolts or detach the tank chain, and remove the column base. Set the hydraulic cylinder lifting switch to the "DOWN" position, and slowly open the pressure regulating valve (at this point, a small amount of methanol can be added to the upper part of the piston head for lubrication). This will allow the packing material inside the column to slowly descend into the container.
Cleaning
If the packing material does not descend smoothly, methanol or another solvent can be slowly added through the inlet at the top, ensuring that the packing material fully enters the container without any residue left inside the column. Once done, close the pressure regulating valve.
Piston Head Removal
Set the hydraulic cylinder lifting switch to the "UP" position and slowly open the pressure regulating valve, allowing the column head to rise at a uniform speed. Once the column head has risen to 20cm above the top of the column, close the pressure regulating valve. Remove the upper piston head for cleaning and storage.
Precautions
- The packing method described in this article is applicable to DAC only. Please make adjustment during operation according to actual needs.
- The machine pressure is high during packing. Be sure to check the position before operation and adjust as necessary to avoid any possible machine damage.
- The reagents used during packing are volatile organic solvents. It is necessary to maintain ventilation in the workplace.
- The machine shall be cleaned after use to avoid any possible corrosion or damage.
Evaluation of Column Performance
After packing, the effectiveness of the column packing is typically evaluated using an LC system, including:
- Verification of the number of theoretical plates (N)
- Assessment of peak shape
If the results of the column efficiency evaluation fall short of expectations, the packing process can be appropriately adjusted in order to achieve optimal performance.