First steps towards a generic sample preparation scheme for inorganic engineered nanoparticles in a complex matrix for detection, characterization, and quantification by asymmetric flow-field flow fractionation coupled to multi-angle light scattering and ICP-MS

Abstract

This paper describes the systematic development of a method to detect, characterize and quantify nanoparticles in tomato soup. It focuses on sample preparation for detection, characterization and quantification of SiO2-engineered nanoparticles (ENPs). Sample preparation aims at a complete ENP isolation from the tomato soup matrix, no alteration in ENPs size distribution and minimal loss of ENPs. Based on the physicochemical properties of SiO2-ENPs and tomato soup two sample preparation approaches (acid digestion and colloidal extraction) were tested. Subsequent particle detection, sizing and quantification were done by Asymmetric Flow-Field Flow Fractionation (AF4) hyphenated with multi-angle light scattering and ICP-MS analysis. Complete matrix removal and Si mass recoveries > 90% was only achieved by microwave assisted acid digestion. The effect of the sample preparation on the size distribution was minimized by optimizing particle stabilization (pH adjustment, tip sonication time). The increase of the average hydrodynamic radius by the sample preparation remained always below 30 %, irrespective of the sample type (pure ENP suspension and ENP in tomato soup). Altogether the chosen analytical is suitable to detect ENP in complete food matrices and might help improving production, labelling and legislation, and food safety.