Filter Media Selection Guide

Membrane Solutions’ superior media separation technology ensures protection of your analytical instruments and supports the integrity of your analytical results. Membrane Solutions’ capabilities ensure:

l Accurate pore size ratings for better chromatography and instrument/column protection.
l Uniform membrane materials (lot-to-lot) to provide consistent analytical results.
l Low extractable materials for less chromatographic interference.
l Materials of construction selected specifically for analytical analysis with lower extractables and lower API adsorption

1. Determine if you need hydrophobic or hydrophilic filters

Consider if filter material should be hydrophobic or hydrophilic based on the solution to be filtered.

Hydrophilic Filters

Possess an affinity for water
Can be pre-wet with virtually any liquid
Are preferred for aqueous solutions

Hydrophobic Filters

Will not allow passage of water
Will wet in low surface tension liquids such
as organic solvents

2. Consider chemical compatibility

Chemical compatibility is defined as the ability of a filter material to resist select chemicals so that the pore structure is not adversely affected by chemical exposure, and the filter material does not shed particles or fibers to add extractables. For example, nylon is not recommended for strong acidic solutions due to incompatibility. The chemical compatibility chart on the back of this brochure will help you make the right choice.

Temperature, time, concentration, applied pressure, and length of exposure also affect compatibility.

3. Choose the rightpore size

Pore size is best selected by considering the instrumentation used for analysis. UV/V spectrophotometers may only require 1.0 μm filtration, where HPLC analysis may require
0.2 to 0.45 μm filtration due to the size of the beads in the column packing and internal frits. The filter material’s pore size is determined by the diameter of the smallest particle that is to be retained with a defined, high degree of efficiency.

For standard liquid chromatography systems using columns with 5 μm or larger packings, the filtration industry standard is 0.45 μm for syringe filters and mobile phase membranes.
For columns with packings smaller than 5 μm, microbore columns, or when concerned about microbial growth, a 0.2 μm filter is recommended.

To clarify samples or when processing difficult-to-filter solutions, 1 to 5 μm pore sizes or glass fiber filters are suggested. Prefilters generally precede smaller pore size final filters and allow the user to process larger fluid volumes before the filter plugs.