An assessment of the suitability of different types of microfilters for use with protein containing solutions

It was noted while clarifying diluted sera for protein estimations by laser nephelometry that certain types of microfilters absorbed immunoglobulin G (IgG). A range of 10 microfilters (0.45 μ pore size) were evaluated for their ability to filter diluted sera (1:100 in saline) without removing IgG or albumin from the solutions. It was found that none of the filters removed albumin. However, most filters containing cellulose nitrate removed between 9–49% of the IgG from diluted sera. The details of this study are presented. The results from this study suggest that microfilters should be selected not only on their ability to remove particles of a nominated size but also on the ability of the membrane to be non-absorbent towards the material being filtered.