Gelatin adsorption at the air water interface as investigated by X-ray reflectivity

The method of X-ray reflectometry with electron density "labeling'' of poly ampholytes by heavy counterions has been demonstrated for measuring the ads orption profiles of gelatin at both hydrophobic (air/water) and like-charge d hydrophilic (arachidic acid) surfaces. The results show that gelatin adso rbs onto a hydrophobic surface with a dense layer corresponding to the chai n diameter, whereas this dense layer is absent for adsorption onto a hydrop hilic like-charged surface. For both surface types a diffuse and extended a dsorption layer is found.