Chemicals from customers' returns have to be analysed before they can be reused as raw materials in production. A procedure for non-invasive qualitative analysis of compounds in a closed container based on energy dispersive X-ray fluorescence (EDXRF) spectrometry is described. EDXRF was chosen as method for non-invasive analysis of chemicals through PE bottle walls without opening the bottle. This analysis aims for a quick proof of correspondence between the declaration of a reagent on the label of the bottle and its content. This analytical result cannot be achieved by a mere evaluation of characteristic element lines in EDXRF-spectra in combination with the method of matrix correction or the method of mean atomic number. These procedures take into account only a small part of the total information available in an X-ray spectrum. It is shown here that valuable additional information is extractable from the spectral ranges of the Compton-scattering and Rayleigh-scattering areas by the use of methods of multivariate data analysis, especially by Principle Component Analysis (PCA). Regularized Discriminant Analysis (RDA) was employed to establish a classification scheme for unknown samples.