FAST AND EASY INTERPRETATION OF A SET OF ABSORPTION-SPECTRA - THEORY AND QUALITATIVE APPLICATIONS FOR UV EXAMINATION OF WATERS AND WASTEWATERS

The isosbestic point of a set of absorption spectra is often the only sign for the simple interpretation of a phenomenon: the presence of two components or eventually two mixtures with a fixed relation between their concentrations. Unfortunately explanations in the literature are not complete so that they can lead the chemist to wrong interpretations. This work presents an exhaustive theory for the interpretation of the existence of one or several isosbestic points and secondly proposes a much more general method to find relevant informations among a lot of absorption spectra: this method based on the rank determination of the data matrix is simple and fast and allows to find the independent spectra from which all the others can be computed by a linear combination. So, the number and the nature of the spectra of the reference components - or mixture - of all the samples can easily be known. Some qualitative applications for UV examination of natural waters and wastewaters are presented to show the importance of the proposed method and the similarity between the reference spectra of waters of different nature.