The energy loss near edge structure (ELNES) of many elements is strongly influenced by the presence of oxygen or other elements at surfaces, grain boundaries, or in the bulk material. The presented investigation deals mainly with the influence of oxygen at the surface. A method for the separation of both, the pure bulk signal and the oxidized surface signal, was evaluated and tested on Al, Cu, Mg, and Si. A comparison of experimental data with ab initio bandstructure calculations and other proofs of the accuracy of ELNES separation are presented. Influences of error propagations were tested and are exemplarily given for Al and Si.