PTFE Filters

Two new PTFE filter membranes are introduced – M3 and M4 oleophobic values. Based on our proven hydrophobic PTFE membrane, the new value is actually hydrophobic and oleophobic. This means that its use will prevent water-over water and oil provide further protection to analysis.

Want to test it on your sampling system? Tell us and we will send you to try.

What is the PTFE membrane?

We are happy to launch this but what if you don’t know much about what they use, or where they will make the most of the difference? I thought I would take this opportunity to give an introduction to the PTFE membrane.

Introduction to PTFE membranes

The classic filter first introduced the PTFE membrane in 2002. They are most commonly used in sample systems to protect expensive and sensitive analytical equipment. Because they are hydrophobic water rejected from the surface and membrane pores and cannot pass.

The new Oleophobic membrane was introduced to add new dimensions to the protection level by preventing the passage of oil and water.

What is the PTFE Oleophobic membrane function?

Their main goal is to eliminate oil droplets and aerosols from gas samples even though they mentioned they also use water too.

When does the PTFE oleophobic membrane need to change?

The PTFE Oleophobic membrane has an age that depends on the solid level in the sample system. If the sample is clean and the only function is to remove oil and water then service life will be much longer. If there is a high level of solid particles present, service life can be increased by using disposable microfiber filter elements as a pre-filter – a combination ideal for this.

Can I replace the PTFE membrane?

Replacing them as simple as our regular membrane house – all connections are set on the head so that the tube fittings do not need to be dismantled.

And there – introduction to PTFE membranes.

Difference between hydrophilic membranes and hydrophobic membranes

Hydrophobic membranes, such as polytetrafluoroethylene (PTFE) will reject the watery sample, creating back pressure. Although sometimes it is possible to overcome this back pressure with additional strength, there is an incomplete risk of membrane and filtration.

If there is no alternative, pre-wetting membranes with alcohol can reduce this back pressure effect.

PTFE and other hydrophobic materials are very suitable for organic and solvent samples, which produce pressure or back pressure. However, some organic solvents can absorb membrane material, especially when contacted for a long time.

This absorption makes ingredients swell, reduces the size of the pores and affects the performance of the filter. Some solvents may also chemically attack material, release extracted into the filtrate. In rare cases, solvents may be partly or full of membranes, resulting in breakthroughs and potential contamination of samples.

Depth Filtration

In terms of particle retention, filters fall into two categories: surface filters and depth filters. Surface filters, generally referred to as membranes, trap particles exclusively on the upper surface. This filter is perfect for samples with low particulate content. However, high particulate content tends to clog the filter surface quickly.

Encourage high particulate samples through surface filters, such as track-etched polyester, the possibility of producing backward pressure and the possibility of breakthrough with sufficient strength. The depth filter on the other hand, is perfect for high particle applications, trapping particles in their fiber matrix.

Asymmetrical depth filters, made of material such as polyether sulfone (PES), have an open matrix structure at the top, and the structure of the matrix that is finer down. This porosity gradient initially trapped large particles and acted as a pre-filter for more dense ingredients below it, maintaining the flow.

For samples that are difficult to filter with high particles, such as soil samples, non-woven matrix filters provide a fine filtration of heavy duty. Polypropylene non-woven (NWPP), for example, provides high endurance and loading capacity for particles.

Binding protein and sample extract

In addition to resistance and blockage, membrane sample compatibility affects the composition of the filtrate. The incompatibility here can cause an unexpected sample barrier to be maintained by a filter (protein binding) or unwanted solute released into the sample (extracted) of the filter or housing material.

Certain hydrophilic materials, such as nylon (NYR) and cellulose nitrate (CN), provide high protein binding capacity. This property makes them not suitable for recovery and protein analysis, where its use can produce inconsistent or unexpected results.

However, cellulose regeneration (RC) and cellulose acetate (CA) bind almost no protein, making it very suitable for filtering solutions containing protein. RC also has extensive solvent compatibility. Together with PTFE, RC is a common purpose option that is useful for sizes.

Extraction is a common symptom in membrane samples and influencing sensitive downstream analytic techniques, such as ultra-high performance liquid chromatography (UHPLC) and high-performance liquid chromatography (HPLC). PTFE, Polyvinylidene Difluoride (PVDF), and RC is compatible with various solvents commonly used in HPLC while remaining low in extraction.