In routine sample filtration, compatibility of the filter material is frequently disregarded. When choosing filter paper or other tools, researchers prefer to do so out of convenience and only change their minds after a failure or debugging an unexpected result.

It is possible to choose from various Membrane Filters materials, such as glass or natural and synthetic polymers, each of which has specific features that make it compatible with practically every sample.

Generating a comprehension of these characteristics and establishing a preventative approach for filtration and membrane-sample compatibility can help reduce the time spent troubleshooting and increase the efficiency of the filtration.

Hydrophilic and Hydrophobic Membranes Have Different Properties

Any aqueous sample will resist a hydrophobic membrane, such as polytetrafluoroethylene (PTFE), leading to back pressure. The risk of membrane rupture and insufficient filtration exists even though it can occasionally counteract this back pressure with added force.

Organic samples and solvents work well with PTFE and other hydrophobic materials because there is no resistance or back pressure. However, some organic solvents can seep into the membrane material when in contact for extended periods.

The material swells due to this absorption, which reduces the pore size and affects the filter's effectiveness. A few solvents may also damage the substance chemically, releasing extractable into the filtrate. Rarely, a solvent may partially or entirely disintegrate the membrane, leading to breakthrough and possible sample contamination.

Most membrane materials, especially hydrophilic ones, are unlikely to be harmed by aqueous samples. However, pH has a significant impact on how compatible a membrane is.

Very acidic or strongly alkaline solvents might not harm a membrane immediately, but they can have an impact over time. Therefore, only highly inert membranes like PTFE are appropriate for high and low pH samples.

Depth Filtration

Surface and depth filters are the two types of filters that can retain particles. Surface filters, sometimes known as membranes, only catch particles on the top surface. Low particle sample types are well suited for these filters. High particle content, however, tends to clog the filter surface quickly.

If enough power is applied, pushing a high-particulate sample through a surface filter like track-etched polyester will likely cause back-pressure buildup and possible breakthroughs. On the other hand, depth filters are ideal for high-particulate applications because they can trap particles inside their fiber matrix.

Asymmetric depth filters contain an open matrix structure at the top and a finer matrix structure toward the bottom. These filters are built of materials like polyethersulfone (PES). This porosity gradient maintains flow by initially trapping big particles and serving as a pre-filter for the denser material below.

Non-woven matrix filters offer powerful fine filtration for difficult-to-filter materials with significant particle content, such as soil samples. For instance, non-woven polypropylene (NWPP) offers strength and a high loading capacity for particles.

Non-woven matrices are typically thick pads with layered architectures used to reduce clogging. Glass fiber and cellulose are additional materials you can use to make non-woven matrix filters.

Protein Binding and Sample Extractable

The membrane's compatibility with the sample impacts the filtrate's composition in addition to resistance and clogging. Here, an incompatibility might inadvertently cause unintended solutes to be released into a sample (extractable) or unintended solutes to be held by the filter (protein binding).

Some hydrophilic substances, such as nylon (NYL) and cellulose nitrate (CN), have a high potential for binding proteins. Because of this characteristic, they are inappropriate for protein recovery and analysis, where their use can produce erratic or unexpected results.

Regenerated cellulose (RC) and cellulose acetate (CA), on the other hand, bind almost no protein, making them ideal for filtering solutions that include protein. A wide range of solvents is compatible with RC. RC is a helpful all-purpose material to keep on hand along with PTFE.

Incompatible membrane samples are frequently characterized by extractables, which impact delicate downstream analytical procedures like ultra-high-performance liquid chromatography (UHPLC) and high-performance liquid chromatography (HPLC). Even though they are low in extractables, PTFE Filter, polyvinylidene difluoride (PVDF), and RC are compatible with various typical HPLC solvents.

For convenient reference, we have created compatibility charts that list a material's resistance to popular solvents. The possibility of problems like sluggish or ineffective filtration, or sample contamination from extractables, is reduced, and filtration efficiency is increased when filter material is chosen based on compatibility.

Contact Simsii support for guidance on the qualities and compatibility of membrane Filters materials. Alternatively, you can find the best filter material for your application. Simsii is a well-known private supplier of laboratory filtration products, including membrane filters and syringe filters made of nylon, PES, PTFE Filter, PVDF, MCE, PP, CA, and glass fiber, among other materials. Both domestic and foreign businesses can purchase high-quality lab filters from our Simsii.