Quantification of XPS spectra of insulating core-shell nanoparticles provided by University of Eastern Piedmont Amedeo Avogadro (PMO) has been performed with help of the National Institute of Standards and Technology (NIST) database for the simulation of electron spectra for surface analysis (SESSA) and the data processing program CasaXPS. The preparation of the NP, which were delivered in liquid suspension, was done in-house and documented. The XPS spectra were recorded by a system designed and constructed by SPECS Surface Nano Analysis GmbH and the problems faced during the measurement such as partial charge effects are outlined. Especially, the shell thickness was determined by a direct and non-iterative method, which was developed by Alex G. Shard. Also, a sample of a planar IRGANOX overlayer on 50nm Au was quantified and investigated the behaviour of the background spectrum of the respective XPS spectra. Knowledge about the origin of the background provides information about the morphology of not only planar layered specimens, but also of core-shell nanoparticles. For a better understanding of the energy losses the electrons experience during their travel through the solid, the single inelastic bulk scattering probability DIIMFP was determined with help of REELS measurements and a simple deconvolution method.