Recommend a filter membrane

[Cliff Mitchell]

Hi
Could someone recommend a membrane for mobile phase filtration? I don't necessarily need a brand name as much as the specifications. I am looking for info on porosity (.45um, .22um) and media type (nylon, nitrocellulose, other), and solvent compatibility.

We do pretty standard reverse phase stuff, meoh/water acn/water mobile phases, sometimes with phosphate, or volatile MS buffers like ammonium formate, acetate, or TFA. We also do normal phase work too, IPA/hexane, so ideally the membrane will be compatible with a wide range of solvents.

We had to move to our operation to a "new" room that hasn't been used in about 5 years, so there is a fair amount of dust in the air.

Thanks
Cliff

[Dan]

Cliff,

Typically you would use a filter with a 0.45 micron pore size. With the filter devices commonly in use today, there are two sizes of filter membranes: 47 mm and 90 mm diameters. Using the 90 mm size can give you a faster filtration. These devices use either a sintered-glass frit or a stainless-steel screen to support the filter membrane. The sintered-glass frit may or may not be removable and it's not my first choice as it can be difficult to clean as it is easily contaminated and clogged (example: ion-pair reagents don't clean off this frit easily). I recommend using the stainless-steel screen; it is removable and easy to clean.

Filtering a mobile phase with TFA is not a good idea as the TFA is very volatile and can be lost during filtration.

The most common filter membranes are made of nylon, PVDF and PTFE. Each of these is compatable with a wide variety of solvents. The choice of the three depends on the solvent composition/polarity. Nylon is good for aqueous/organic mixtures when the organic percent is no more than about 30-40%. With higher percent organic in the mix, go with the PVDF. PTFE is good for mostly or all organic/non-polar solvents/mixtures.

These are some general guidelines. I hope it helps.

Regards,
Dan

[Cliff Mitchell]

Thanks for teh info

[HW Mueller]

We have also been using regenerated cellulose microfilters for aqu./org mobile phases. No problem, just use a bit of the liquids to wash assembled filter, funnel, flasks...

[DR]

We've had good luck w/ Pall P/N 66608 47mm Nylaflo filters (0.45µ)