Yes, “Best Practices” for using any Syringe Filter is to dispose of the first few milliliters that comes through the Filter.
If there are any Extractables or if there is going to be any adsorption to the Membrane, it will usually happen in the first few milliliters. This is called bringing the filter to a “Steady State”. This may be causing your differences.
For 25mm devices you should not use the first 2-5 milliliters and for the 4mm device, you should discard of the first 0.5ml.
MicroSolv Filters Equivalency.pdf 26.9 Kb Download File