Desenvolupament d’un mètode analític per a la determinació d’impureses inorgàniques en (micro)-plàstics mitjançant micro-fluorescència de raig X (μ-XRF)

Abstract

The presence of (micro)-plastics in different aquatic environments is a matter of world concern that has been gaining importance in recent years due to its potential impact on the environment and human health. (Micro)-plastics have been found in practically all types of water bodies and the presence of metals in these materials, either due to their manufacture or through adsorption processes, can be very harmful. Some toxic metals such as Pb, Hg, Cd and Cr present in (micro)-plastics can be released into the water and this fact can negatively affect ecosystems due to their persistence. The most commonly used methods for the determination of metals in (micro)-plastics require carrying out acid digestions with microwave ovens and subsequent analysis with spectroscopic techniques and therefore require a previous treatment of the sample in which dangerous and harmful reagents such as strong acids and oxidizing agents are used. The main objective of this work is the development of a non-destructive analytical methodology focused on the use of X-ray fluorescence spectroscopy (XRF) for the multi-elemental analysis of (micro)-plastics. In order to develop this method, it was necessary to determine the elemental composition of a set of plastic samples through their digestion and subsequent analysis by means of ICP-OES, in order to use them as standards to calibrate the micro- XRF. Once the quality of the results obtained with the methodology developed through the analysis of certified reference materials was verified, the method was applied to the analysis of (micro)-plastic samples from the Mediterranean Sea and the Atlantic Ocean. The results obtained have been promising and the determination of metals in the samples has been achieved without the need to treat previously the sample. It has been observed that the elements most present in these samples are Ca, Ti, Fe, Cu and Zn. However, in some samples it was also possible to determine appreciable contents of more toxic metals such as Cr and Pb. In addition, the elemental distribution has been studied in some of the samples studied and it has been possible to verify that this is not homogeneous