Evaluating the photocatalytic treatment of stevioside by TiO2 in different aqueous matrices and identification of transformation products

• Published in: The Science of the total environment 2017-12, Vol.607-608, p.568-577
• Main Authors: Sakkas, V.A., Sarro, M., Kalaboka, M., Santoro, V., Albanis, T., Calza, P., Medana, C.
• Format: Article
• Language: English
• Subjects: Experimental design; Intermediates identification; Photocatalysis; Stevioside; Sweeteners
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.07.016

The present study reports the photocatalytic transformation of stevioside, under simulated solar irradiation using TiO2 as a photocatalyst. As a tool of investigating the effect of various aqueous matrices, as well as, the initial stevioside concentration on the variation of the photocatalytic efficiency, a fully nested experimental design was employed. A significant impact on the degradation rate of the sweetener was observed: degradation rate decreases in the order distilled water>river water>lake water, attributed to the increased natural organic matter content of the respective natural water samples. Moreover, the investigation has involved the identification of intermediate compounds, as well as the assessment of mineralization and toxicity evaluation. More than one hundred unknown transformation products, most of them in the form of several isobaric species, were identified. By employing accurate mass determination, we were able to attribute an empirical formula to each species and through MSn analyses we were capable to distinguish several isobaric species. The overall transformation mechanism was assessed and involved the hydroxylation/oxidation of the molecule and the subsequent loss of the glucose units bound to the parent compound. [Display omitted] •Photocatalytic transformation of stevioside using titanium dioxide•The effect of various aqueous matrices and stevioside concentration was assessed.•A fully nested experimental design was employed.•More than one hundred unknown transformation products were identified via HPLC-HRMS.•Assessment of mineralization and acute toxicity using Vibrio Fischeri was performed.