The method of standard additions was performed in order to determine the amount of PDMS present at the surface of a dehydrated hydrogel material. Known amounts of a PDMS monomer were added to the surface and allowed to equilibrate. Peak ratios of 73Da (C3H9Si+):69Da(C4H5O+) and 147Da(C5H15Si2O+):113Da(C6H9O2+) were plotted against ng of PDMS added to the surface. A linear fit was applied to the data and the amount of PDMS present at the native surface was determined.