User Guide: Amicon^® Stirred Cells

Introduction

Amicon^® Stirred Cells are designed for rapid concentration and/or diafiltration of macromolecular solutions. Used in conjunction with an external compressed gas source and a magnetic stirrer, the stirred cells provide high concentration factors and high sample recovery. They are ideal for desalting or buffer exchange applications and can be used in either continuous or discontinuous diafiltration mode.

Amicon^® Stirred Cell Features

• Pressure-driven filtration coupled with magnetic stirring provides a gentle method for concentration and reduces shear-induced denaturization of biological samples.
• Magnetic stirrer positioned at the filtration interface greatly minimizes the risk of concentration polarization and subsequent fouling of the membrane.
• Three sizes offer a broad range of process volumes (up to 400 mL) that can be further expanded with the addition of an external reservoir.
• The flexible, easy-to-use design can accommodate a wide range of ultrafiltration and microporous membranes at varying pressures and temperatures.
• Minimal holdup volume and easy sample recovery.
• Autoclavable for sterile applications.

Models Available

Product No.	Maximum Working Volume	Membrane Diameter
UFSC05001	50 mL	44.5 mm
UFSC20001	200 mL	63.5 mm
UFSC40001	400 mL	76 mm

NOTE: Minimum concentrate volume must be determined empirically by the user since it depends on sample composition and stirring speed.

Operating Modes

Stirred cells can be operated in either a concentration or diafiltration mode. In concentration mode, gas pressure is applied directly to the stirred cell. Solutes larger than the membrane’s molecular weight cutoff (MWCO)/pore size are retained in the cell, while water and solutes smaller than the MWCO/pore size pass through the membrane into the filtrate.

Diafiltration is a fast and efficient technique for desalting as well as buffer exchange of solutions. It can be performed in a batch (discontinuous) or constant volume (continuous) mode.

Discontinuous Diafiltration: The sample is first concentrated to a fixed volume, then diluted back to its original starting volume with water or buffer. Conversely, the sample can be diluted to a fixed volume with water or buffer, then concentrated back to its original volume. Either process is repeated until the remaining salt or solvent is removed or lowered in concentration.

Continuous Diafiltration: Buffer salts are removed, exchanged, or lowered by adding water or exchange buffer at the same rate as the filtrate is collected. Continuous diafiltration is gentler and more efficient than discontinuous diafiltration, as it maintains product stability by keeping the sample concentration and volume constant during diafiltration.

The Amicon^® Stirred Cell Reservoir (6028) or Dispensing Pressure Vessel (XX6700P01) can be used for diafiltration applications and to increase the volume capacity of the stirred cells. In continuous diafiltration mode, the reservoir/pressure vessel containing diafiltration solution is connected to the stirred cell and gas pressure supply via the Amicon^® Stirred Cell Selector Valve (6003) or similar user-supplied valve(s). The selector valve allows instant switching between concentration and diafiltration modes without interrupting system operation. The combination of an external reservoir and the Amicon^® Selector Valve create a simple diafiltration system that keeps the stirred cell fluid volume and macrosolute concentration constant as the filtrate volume is replaced by the diafiltration solution. In either mode, the Amicon^® Stirred Cell Manifold (6015) can be used to operate multiple stirred cells in parallel.

Amicon^® Stirred Cell Components

Materials Required but Not Supplied

• Ultrafltration or microfltration membrane discs
• Magnetic stirrer
• Source of clean, regulated, compressed air or nitrogen with tube fttings/connectors appropriate for connecting to ¼ in. outer diameter (OD) tubing at the desired operating pressure
• Collection containers

Pressure Limitation

Do not operate the stirred cell above 5.2 bar (75 psi).

Assembly and Operation

Concentration Mode

1. Snap membrane holder onto base.

2. Place membrane into membrane holder, oriented as indicated in membrane instructions (shiny side up for ultrafltration membranes). Place O-ring on top of membrane and push down gently to seat membrane in holder.

NOTE: See membrane instructions for rinsing and chemical compatibility. Handle membrane by edge to avoid scratching or contaminating surface.

3. Align filtrate port on membrane holder with slot in bottom of cell body. Screw base into cell body.

4. Attach filtrate tubing assembly to filtrate port on membrane holder.