Most chromatography grade syringe filters are constructed of either HDPE or PP. These materials are compatible with a wide range of HPLC solvents and both offer low levels of extractables. HDPE has been reported to be more chemically compatible with aqueous basic solutions of NH4OH than PP.
For example, is sterilization of the fluid the goal? If so, a 0.22 micron filter is generally accepted as the best choice.
For most chromatography or LC-MS applications either a 0.45 or 0.22 micron filters are preferred.
- Please refer to the various manufacturers data sheets to select an appropriate syringe filter with: (1) a low hold-up volume; (2) large enough size for the volume of sample; (3) which is chemically compatible with the solution and material you are going to inject through it and (4) lowest protein binding affinity (if applicable).
- To reduce the hold-up volume, use a post-filtration air purge to empty the filter.
- Minimize contamination from extractables (in the plastic) by pre-rinsing the filter membrane with some of the clean solution. This can reduce the amount of detectable extractables in your sample. PTFE based membranes have some of the lowest extractable levels so consider their use if this is an issue.
- If analyte binding is a concern, select one of the membranes which has the lowest binding affinity such as PVDF or PTFE.