What syringe filter is the best for my application?

There is a huge selection of syringe filters available in all kinds of material, pore sizes and diameters.  When it comes to selecting the most appropriate one for your application this can make it seem like a bit of a minefield. We break the process down into a number of steps to help simplify selection.

1. Match pore size with your application

Most types of syringe filters come in a selection of pore sizes. Ensuring the pore size is suitable for your application is highly important to ensure it functions as you desire. Below are the most common pore sizes found in our range and examples of typical applications.

• 0.1μm - solution sterilisation and mycoplasma removal
• 0.2/0.22μm - solution sterilisation (bacterial removal)
• 0.45μm - general filtration and particle removal
• >0.45μm - typically used for pre-filtration

2. Select the most appropriate filter material based on your sample type and downstream analysis method

Syringe filters are composed of a membrane filter contained with plastic housing (usually polypropylene). Each membrane has a number of key physical and chemical characteristics that make it suited to a certain type of application. In the table below, we summarise some of the key properties of each and the most common applications you will find them used in.

Table of properties:

Membrane Material	Protein binding	Hydrophilic Hydrophobic	Chemical resistance	Applications
Hydrophilic PTFE	Low	Hydrophilic	High	Purification of HPLC organic and solvent/aqueous solutions
Hydrophobic PTFE	Low	Hydrophobic	High	Filtration of solvents
PES	Low	Hydrophilic	Low/Medium	Purification of tissue culture solutions, buffers
PVDF	Low	Hydrophilic	Medium	Filtration of protein solutions
NYL	Medium	Hydrophilic	Medium	Filtration of aqueous and solvent/aqueous mixtures
CA	Low	Hydrophilic	Low	Filtration of protein solutions
CN	High	Hydrophilic	Low	Filtration of aqueous solutions where protein binding is not a concern and microbioloigical applications.
RC	Low	Hydrophilic	Medium	Filtration of aqueous and organic solvents and protein recovery applications.

3. Select diameter based on your sample volume

High particulate loaded samples with tend to block the pores in the membrane more quickly so the total volume you can filter through a certain diameter syringe filter will vary greatly. Please take the below figures as a guide only.

• 13mm diameter - for samples <10ml
• 25mm diameter - for samples <100ml
• 33mm diameter - for samples <250ml

4. Select syringe fitting

Most syringe filters with come with the standardised Luer fitting - either Luer Lock or Luer Slip.

• Luer Slip - will fit on to any Luer fitting syringe. Simply 'slip' the filter onto the end of your syringe. It is quick to add and remove from the syringe
• Luer Lock - will only fit onto a Luer Lock syringe. The filter locks into place and this allows for a greater pressure to used with the filter popping off like it would do on Luer slip.

Other syringe filters or inline filters may come with different types of fitting such as stepped barb.

5. Do you need pre-filtration?

Combine a high level of particles with a very fine pore size and its a recipe for your filter to get clogged up without actually filtering down to the particle size desired. The answer to this is using pre-filtering. Pre-filtration uses a filter (often glass microfibre) with a lot larger pore size than that of the filter contained in the syringe filter to 'remove' the bulk of the larger particles that will clog your filter. This can be done separately to the syringe filtration itself or the pre-filter may come 'built in'. Read more here.

Where can I buy?

Camlab stock a wide range of syringe filters from world leading manufacturers. If you select the filters down the left hand side of the web page, it will help narrow down your selection. If you are struggling to locate the right syringe filter, please contact us with answers to the above questions and we will point you in the right direction. You can also email support@camlab.co.uk for assistance.