Surface and depth profile investigation of a phosphorylcholine-based contact lens using time of flight secondary ion mass spectrometry

The dehydrated surface of a commercially available contact lens containing hydroxyethyl methacrylate and phosphorylcholine is investigated by time of flight secondary ion mass spectrometry employing a 25 keV Bi-3(+) ion beam. Results show the successful detection of hydroxylethyl methacrylate and phosphorylcholine species from an Omafilcon A lens. Utilization of a 20 keV C-60 ion beam allowed the bulk region of the lenses to be probed using primary ion dose densities exceeding 2 X 10(14) C-60/cm(2) and indicated that the phosphorylcholine component reorganizes below the surface. X-ray photoelectron spectroscopy results are consistent with the presence of these moieties and suggest that the phosphorylcholine components may be below 100 angstrom in the dehydrated hydrogel. (c) 2007 American Vacuum Society.