The mass of five proteins (Bovine serum albumin (BSA), casein, lysozyme, ovalbumin and pepsin) adsorbed to five different membrane materials (of various hydrophobicities) was quantified using a static system and analysed to establish any trends. Comparing the results from the five membranes it seems that there were no obvious trends between the protein masses adsorbed indicating that it may not be just one aspect of protein structure that is important in the adsorption process. Many investigations have indicated that the protein may undergo a conformational change during the adsorption process. Disulphide bridges contribute readily to the stability of the protein molecule and it was hypothesised that if such a structural change occurred, it would result in the breakage of these covalent bonds. To this end, the free thiol group content of the proteins was quantified before and after adsorption.