When selecting a syringe filter you have two choices: hydrophobic filters or hydrophilic filters. Both serve a very different purpose and we want to help you make a decision on which to choose to best serve your needs. Before you make a choice about what filter to use you first have to understand what makes these filters different.
What does Hydrophobic and Hydrophilic mean?
Hydrophobic, means exactly what it sounds like, a phobia of hydro. A hydrophobic filter will be water repelling making it ideal for gas filtration. A hydrophobic filter will have a ‘phobia’ of water.
Hydrophilic, similarly, sounds a lot like its meaning. Hydrophilic filters are water attracting and the most popular choice for the filtering of an aqueous solution. A hydrophilic filter has ‘love’ (philic) for water.
A basic breakdown of these words as they pertain to not just syringes, but a variety of topics, can be found here.
But let’s break that down a little more…
Hydrophilic Membrane Syringe Filters
Water-loving filters are the usual choice for the filtering of liquid based solutions. This makes sense on the surface. But how does this really work?
A hydrophilic syringe filter removes particles from an aqueous sample. This is helpful to purify and sterilize aqueous solutions so that they do not damage equipment. Hydrophilic syringe filters are imperative when using precious equipment. The surface chemistry of the hydrophilic membrane allows for the surface to be saturated by the liquid.
An example of hydrophilic filitation would be removing bacteria from an IV solution.
Hydrophobic Membrane Syringe Filters
Water-hating filters are the right choice for a gas filtration process. Once again, we can assume this from the structure of the word. How does this work?
A hydrophobic membrane syringe filter allows gasses to interact more effectively and keeps liquid substances out. These membranes will not wet in water allowing for efficient and safe usage.
An example of where these filters are helpful would be in dealing with gasses in a medical setting.
How do I know which membrane filtration is best for me?
Choosing the correct membrane filtration style is very important for the sake of your equipment and the safety of your work. Obviously there are more choices when you get past hydrophilic or hydrophobic. You have to consider connection type, membrane material, pore size, diameter, and whether or not the filter is sterile.
- Connection Type- syringe filters most commonly have a female luer lock inlets and male luer lock outlets, however they can also be outfitted in the reverse. A threaded connection with a male outlet and a female inlet are designed to provide a sturdy and trustworthy seal.
- Membrane Material- choosing the correct membrane material is entirely dependent on the chemicals and solutions you’ll be working with. Flow rate, chemical compatibility, and binding factors are all important to consider. We have helpful charts here and here to help you determine what is best for your work.
- Pore Size- this is determined by the size of the particles you need to filter out. The finer the pore the more pressure needed to push through the filter.
- Diameter- this will be determined by the size of your sample. Use a membrane filter with a greater membrane area if you are planning on using a high volume of solution.
- To sterilize or not to sterilize? – that is the question! Whether ‘tis nobler in the mind to….the reference is falling apart here. Choosing a sterile or non-sterile option is dependent on your samples processing application. To insure your work does not fall apart like our ill-thought out reference we offer both sterile and non-sterile options.
Are there any exceptions to the rule here?
Actually, yes! Some hydrophobic filters can be used in liquid filtration. As long as the liquid is a lower density and surface tension than water.
And sometimes a hydrophilic filter can be used when condensation builds up over time.
These exceptions allow hydrophilic filters to be used in circumstances where a hydrophobic application was previously used and a hydrophobic filter to be used where you may think you need a hydrophilic filter.
In science everything is…well a science! There is always a circumstance that requires special attention.
How do I know if a membrane I have is hydrophobic or hydrophilic?
You can test an existing membrane simply by using a droplet of water on the surface. Whether it soaks into the surface or suspends on the surface will tell you if this membrane is hydrophobic (suspends) or hydrophilic (soaks). This is an easy and effective way to know what kind of membrane you are dealing with.
I have an idea of what filter I need, what next?
Choosing the correct filter for your needs is absolutely imperative to the safety, security, and integrity of your work. We are here to make sure you can make an informed choice that is correct for you and your team.