Frequently Asked Questions
Lab ultrafiltration is a process which uses semi-permeable membranes to separate macromolecules from microsolutes. As transmembrane pressure is applied, microsolutes pass through the membrane while macromolecules (with higher molecular weight) are retained. Typical applications include concentration, diafiltration (buffer exchange | desalination) and fractionation. Ultrafiltration is a gentle, non-denaturing purification method, which is more efficient and flexible than alternative techniques such as chromatography.
When choosing an optimal ultrafiltration device, a good starting point is to consider the size of your target molecule. We recommend choosing a MWCO up to a maximum of 1/3 to 1/2 of the target molecular weight. Also take account of the device capacity, based on initial sample volume. Other factors to consider include whether a particular membrane material or mode of operation is necessary – for example, pressurized ultrafiltration offers increased transmembrane pressure consistency, which can be more suitable for targets prone to aggregation or denaturation.
Cellulose triacetate (CTA) is ideal in applications where the filtrate is of primary interest.
Polyethersulfone (PES) is preferred for low fouling and exceptional flux with most solutions and especially high recoveries of negatively charged target molecules.
Regenerated cellulose (RC) is suitable for general samples and particularly for oligonucleotides and peptides. Finally, Sartorius’ patented Hydrosart® (HY) — a more chemically robust version of RC — is typically recommended for the highest recoveries of very valuable samples such as immunoglobulin G (IgG).
Lab ultrafiltration devices are primarily used with biological samples but can also be used in environmental monitoring and industrial applications. We provide comprehensive compatibility tables for each product in the instruction manuals. For the greatest chemical compatibility, Vivaspin® Turbo devices are recommended.
With Sartorius Lab Ultrafiltration, there is no need for expensive process-scale systems for ultrafiltration of larger sample volumes in R&D labs. Vivaspin® 100 and Vivaflow® cassettes enable convenient processing of samples in the 20 mL to 5 L range with minimal equipment requirements.
The integral dead-stop is the minimum volume to which a sample can be concentrated. For even greater control, it is possible to pre-fill the filtrate tubes of Vivaspin® 500 and Vivaspin® Turbo 4 and 15 devices to prevent over-concentration or avoid the need to re-dilute samples after ultrafiltration.
Optimizing your process to suit each target molecule should be a priority since the same membrane material and orientation, MWCO and device combination may not be ideal for every sample. Start by selecting a MWCO up to 1/3 or 1/2 the size of your target. Test different membrane materials and device types where possible. Also try pre-treatment methods such as pre-rinsing or passivation, and refer to Sartorius’ extensive application guides and expertise to identify the right solution for you.
Yes! While all ultrafiltration devices can be used for this application, Vivacon® devices - featuring horizontal Hydrosart® membranes - typically achieve the highest recoveries from nucleic acid samples. PCR-grade options are also available for worry-free processing in critical applications, such as forensic sample preparation.
It can! Sartorius provides a convenient conversion table to choose a MWCO up to 1/3 the diameter of the target virus. For example, high recoveries of Lentivirus - which has a diameter of ~90 nm - are achieved with 300 kDa MWCO Hydrosart® or 100 kDa MWCO PES membranes.
Typically, the performance of ultrafiltration membranes will begin to degrade through repeated use. However, Sartorius does offer selected devices - Vivaspin® 100 and Vivaflow® 50R | 200 – which can be used multiple times. For these products, robust cleaning and correct storage procedures must be followed, and these are described in the instructions for use.
