Membrane Chromatography FAQ

Information applicable to use of Pall membrane chromatography devices.

How long can Mustang® capsules be stored in or exposed to water?

We do not recommend storing Mustang® Q capsules in water. The Instructions for Use (IFU) detail the procedure to properly store the capsules. The recommended storage solution is 0.1 M NaOH/1 M NaCl.


Water is not recommended because of the possible swelling of the membrane that might result in high pressure drop. However, if the membrane was exposed to water, the effect could be reversed by exposing the membrane to a salt solution with at least 5 mS/cm conductivity. The other concern is related to mitigating pH excursions. As the capsule’s operation is based on an Ion exchange modality, it is essentially for optimum use to operate with salt buffered feedstocks. Flushing the capsule post use with water following the prescribed cleaning and sanitization protocol would not be expected to cause any adverse effect. However, we recommend for any post use capsule storage that the device be flushed with prescribed buffer solution outlined in the IFU.


How do you vent the Mustang® XT Acrodisc® and XT5 Ion exchange chromatography units that have no vent valve?

The Instructions for Use (IFU) detail the procedure to properly wet out the capsules. This will involve priming buffer through the inlet of the capsule upside down, so air is being expunged through the outlet facing up. If air is trapped in the membrane, the binding capacity could be compromised.


The operator is advised not to introduce air into the capsule once the capsule is wetted. If operating either capsule on a liquid chromatography (LC) system, then all buffer and sample lines must be properly primed to ensure no air bubbles are loaded onto the device. In such cases where the likelihood of air being introduced happens during the loading step, we recommend installing a bubble trap inline (for example a three-way valve to release any air) prior to loading into the membrane.  

Are the membrane/housing for Mustang® chromatography devices compatible with 1 N NaOH?

The Mustang® membranes (Q, S, and E) are compatible with 1 N NaOH.  However, the housings used for the disposable formats are stable for one cycle only (30 minutes contact time at 20˚C).


The reusable Mustang® XT capsule formats are all polypropylene and are compatible with several cycles of 1 N NaOH. The number of cycles is sample specific and must be determined by the customer empirically.

What is the recommended flow rate for Mustang® capsules?

10 membrane volumes/min is typical. However, for large molecules such as viral vectors, 5 MV/min or less is typical to prevent a high-pressure drop.

What solution is recommended for long term storage of Mustang® chromatography devices?

Pall recommends a 0.1 N NaOH/1N NaCl solution for storage. For additional details, see the Membrane Chromatography Validation Guides in the Accelerator Documentation Center.

What is the porosity of Mustang® membrane?

Mustang® Q membrane chromatography – 0.8 micron modified hydrophilic PES


Mustang® S membrane chromatography – 0.65 micron modified hydrophilic PES


Mustang® E membrane chromatography – 0.2 micron modified hydrophilic PES

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