Quantification of the adsorption of benzoates on poly(dimethylsiloxane) membrane

We present the first simple, and successful, method to quantify compound adsorption onto a polymer based, skin mimic silicone membrane. Benzoate compounds were selected as adsorbants based on their known controversial safety within the healthcare market. We found that adsorption depends strongly upon the adsorbates chemical structure, more so than silicone membrane thickness. Quantification of adsorption was evaluated through reduction in solution concentration as the molecules adsorbed onto the poly(dimethylsiloxane) membrane. A direct correlation was observed between alkyl chain length and the number of molecules adsorbed per gram of membrane; as the adsorbate alkyl chain length increased, so does adsorption. This finding implies that the hydrophobicity of the adsorbate is directly governing the extent of adsorption. Calculation of the change in Gibbs free energy associated with the adsorption process (Delta G(abs)) further confirmed a direct correlation between extent of adsorption and chain length. Our data highlights the importance of understanding, and more importantly quantifying, the adsorbate-membrane interaction if such systems are to be used to replace in vivo analysis.