Fluorescence characteristics of aqueous dispersed systems of succinic acid as potential markers of their self-organization and bioeffects in low concentration range

Abstract

Abstract The issue of protecting aquatic ecosystems from biologically active compounds (BACs) such as pesticides and pharmaceuticals detected in aquatic environments at low concentrations has become urgent. Presently, literature provides much information about BACs that at low concentrations cause significant damage to hydrobionts, but a physicochemical explanation for these phenomena has appeared only relatively recently. Experimental findings have shown that diluted aqueous solutions of BACs are self-organized disperse systems, whose disperse phase (nanoassociates) rearranges upon dilution, which is accompanied by nonmonotonous changes in the physicochemical and biological properties of the system. This work introduces the study of fluorescence and UV absorption of aqueous diluted systems of a biogenic succinic acid (SA), used as an antihypoxic and antioxidant pharmaceutical. It is shown for the first time that the fluorescence spectra ( λ e x at 225 nm) of SA systems are informative at the calculated concentrations range from 1 ⋅ 10−17 to 1 ⋅ 10−5 M. The nonmonotonous concentration dependence of fluorescence intensity ( λ e x at 225 nm, λ e m at 350 nm) is in good agreement with the data on nanoassociates’ size, as well as with both the physicochemical properties of SA systems and their biotesting results, which were obtained using the certified procedures for monitoring the toxicity of natural waters and wastewater. The observed coherence between the fluorescence intensity of SA systems and the nanoassociates’ size allows for the conclusion that it may be possible to consider fluorescence as a potential marker of self-organization and bioeffects of diluted aqueous BACs systems.