Page 13 - Filtration Resources

Sterlitech offers a wide selection of membranes that have been pre-cut for use with our Sepa CF II Cells, CF042 Crossflow Cells, and HP4750 Stirred Cells.  However, if you want to cut your own membranes for use with any of these systems, you can follow the simple instructions below. HP4750: For this procedure you will need the following materials: a template (the porous stainless support disk works well for this), the membrane you want to cut, scissors, and a pair of latex gloves. 1. Take your template and place the membrane you want to cut against it.  Be sure to have latex gloves on to avoid contaminating the membrane surface. 2. Cut along the edge of the template with the scissors.  Hold the scissors at an angle towards the center of the template to avoid under-trimming.

Once finished, the membrane should sit perfectly flat on supports without any bending and extend outside of the inner O-ring to avoid leakage.

Sepa CF II Cell/CF042: To cut membranes for the Sepa CF II or CF042,

Here's a short demonstration with Kristina explaining how to cut a Sepa CF Membrane Filter using a steel ruled die:

Is there a product or process video demonstration that you'd like to see? Let us know in the comments!

For a nice overview of some basic questions to ask before you select your liquid filtration medium, take a look at this two page paper from the American Filtration & Separations Society. It starts with clear definitions of permeability and efficiency, and then segues into the importance of compatibility between the filter material and the liquid. One of their good points worth repeating here is that for many types of sampling there are pre-existing industrial or organizational standards to guide you. With most of our membrane, syringe, and capsule filters, you can find this information under the “Application” tab for a particular item. Our resources section is another good place to research this information. Want more help? You can always ask one of our technical personnel for added assurance.

If you've ever worked with a Polyamide flat sheet membrane, there's a good probability that you may have noticed some slight discoloration on the active layer side of the filter, as seen below:  And additionally, this may have caused some uneasy speculation; is it mold? contamination? time to purchase a new membrane? The good folks at Toray Membranes were able to shed some light on this common concern... literally. Brown discoloration can be due to small amounts of residual amine from the manufacturing process.  The amine, (one of the building block compounds used to create the polymer constituting  the polyamide membrane family),  can turn brown with exposure to direct light. This effect doesn't make for a pretty membrane,  but it does not affect the performance of the membrane in any way. Note: if it is in fact mold that you're seeing, you can try irrigating the area with dechlorinated water with a laboratory wash bottle to see if it lifts off.  Any rubbing of the membrane

Of all the membrane disc filter accessories that we carry, the static eliminator probably gets the most technical questions. Whereas items like the cytoclear glass slides and stainless steel membrane filter tweezers are very straightforward in their purpose and operation, how a static eliminator works may not be as intuitive. Static eliminators are used on Polycarbonate or Polyester membranes when they are going to be subject to precise analytical balance measurements that could be affected by the presence of static or dust particles on the filter. Static eliminators can perform this function in a few different ways, such as by using alternating current or by using small amounts of a radioactive element to remove electrons. The static eliminators that we carry use a naturally occurring radioactive element called Polonium-210 (It was discovered by Marie and Pierre Curie and named after Marie Curie’s homeland of Poland) in order to function. This type of static eliminator is referred to

We all know oil and water don’t mix. Same goes for acids and bases. But what about Kerosene and cellulose acetate? Or Trichloroethylene and silver? To answer these questions we have our frequently referenced Chemical Compatibility Chart for general laboratory filtration products. Since using the correct filter material is vital to the success of a separation process we are constantly expanding our knowledge base of chemicals used with our filtration products. We currently have data on over 70 chemicals and their recommendation level for filtration materials such as Polycarbonate, Nylon and PTFE. Curious about a chemical that isn’t listed yet? Just ask us about it we’ll be happy to help you out.