An Essential Guide to Efficiently Packing Dynamic Axial Compression Columns

Dynamic Axial Compression (DAC) columns are advanced preparative chromatography devices that integrate the functionality of column packing machines and chromatography columns. They utilize dynamic axial compression technology to pack, maintain pressure, and unpack columns, ensuring a uniform, tight, and stable column bed throughout use.

This article explores the structure, applications, packing procedures, efficiency testing, precautions, and maintenance of DAC columns, using the WelPacker DAC50 as an example.

DAC technology is widely used for large-scale, high-efficiency separation and purification in laboratories and production facilities. It is particularly suitable for processes requiring reproducible and scalable purification solutions.

• Column Volume:
  V = 3.14 × r² × L
  r: Internal radius of the column (cm)
  L: Column length (cm)
• Packing Material:
  m = ρ × V
  ρ: Bulk density of the packing material (g/mL)
  Due to compression, it is generally suggested to use ~1.1 times the calculated mass. The table below shows the required packing material mass to various specifications of WelPacker DAC when packing a 250 mm bed height.
  

  DAC Specification (mm)	Recommended packing material mass (g)
  50	302
  100	1,209
  150	2,720
  200	4,836
  300	10,880
  450	24,480
  500	30,223
  600	43,520
  800	77,370
  1000	120,000

• Slurry Volume:
  Typically, twice the packing material mass (e.g., 300 g of packing material requires ~600 mL slurry solvent). Isopropanol is a common slurry solvent.

Example:
For a 50 mm DAC column with a 250 mm bed height, packing with 10 μm C18 material (bulk density: 0.56 g/mL) requires approximately 300 g of packing material and 600 mL of slurry solvent.

Proper cleaning ensures optimal performance:

• Column Tube: Remove oil and dust from the inner walls.
• Sieve Plates: Ultrasonically clean to remove clogs.
• Distributors and Seals: Wash to prevent contamination.
• Components: Dry thoroughly before assembly.
• Gas Source: Ensure suitability and stability before packing.

The WelPacker DAC employs H-tree distributors to ensure uniform fluid distribution, achieving symmetric chromatographic peaks.

Key considerations for slurry preparation:

• Use inert containers, filling up to 2/3 of their capacity.
• Mix using ultrasonic and mechanical stirring for ~30 minutes. (Ultrasonic not applicable to fragile materials)
• Ensure good fluidity of the slurry solvent and avoid being too viscous or too thin. The ideal state is that a uniform thin line would flow down if the glass rod was picked out of the slurry.
• For DACs of 300 mm or below, manual stirring can be applied; for above, a mixer is recommended.
• Avoid damaging fragile materials by limiting shear force and time.

Key considerations for column packing:

• Clean all components (inner wall, piston, bottom cap, etc.) with isopropanol after pouring in the material. Ensure no residual contaminants.
• For persistent clogs, soak parts in 1 M sodium hydroxide for 12 hours, followed by thorough rinsing for 1 hour and ultrasonic cleaning for 3 ~ 6 times (10 ~ 15 minutes each). Ensure the final rinse has a neutral pH (~7).
• Adjust the air pressure to set value, vent air from the top, then press the slurry out from the bottom end. Once no more liquid is discharged from the bottom, the packing process is complete.
• Finally, allow the column to stabilize for 30 minutes, and then displace any remaining slurry solvent with methanol (or n-hexane).

After packing, let the column equilibrate under pressure for 30 minutes before testing. Connect the column to the liquid chromatography system, using a recommended flow rate (e.g., 80 mL/min for a 50 mm column). Test column efficiency with 1 mL injections of naphthalene/methanol or toluene/methanol solutions (1 mg/mL).

• Choose an appropriate solvent based on the packing material’s properties.
• Use a suitable pneumatic hydraulic pump and adjust the pressure to ensure even compression across the column bed. For smaller columns, the bed should be compacted within 30 seconds to 1 minute.
• Allow the column to stabilize for 30 minutes after packing. or enhanced performance, flush the column with at least three column volumes of the mobile phase to replace the slurry solvent before testing, minimizing irregularities during the initial runs.

Dynamic Axial Compression columns are indispensable tools in preparative chromatography, offering reliable and efficient separation for various scales. Proper packing, testing, and maintenance ensure optimal performance and longevity. 

Welch Materials strives to provide our clients not only high-quality chromatography instruments, columns, and consumables, but also comprehensive one-stop solutions on separation and purification. For inquiries, please contact our sales team at inquiry@welchmat.com.