Abstract
The interest on deep eutectic solvents (DES) has been increasing. However, the ecotoxicological profile of DES is scarcely known. Also, despite previous studies showed that DES components dissociate in water, none assessed DES toxicity using the classical and adequate models for mixture toxicity prediction - concentration addition (CA) and independent action (IA). This study evaluates the ecotoxicological profile of DES based on [N1111]Cl, [N2222]Cl and [N3333]Cl as hydrogen bond acceptors (HBA) combined with hydrogen-bond donors (HBD) vis. ethylene glycol and 1-propanol, through the Microtox® Acute Toxicity Test. CA and IA with deviations describing synergism/antagonism, dose-ratio and dose-level effects were fitted to the toxicity data. Neither the starting materials nor DES were found hazardous to Aliivibrio fischeri, in this specific case agreeing with the claimed “green character” of DES. Among the starting materials, ethylene glycol was the least toxic, whereas [N3333]Cl was the most toxic (30 min-EC50 = 96.49 g L−1 and 0.5456 g L−1, respectively). DES toxicity followed the same trend as observed for the salts: [N1111]Cl-based DES < [N2222]Cl-based DES < [N3333]Cl-based DES. The IA model, with specific deviations, adjusted better in 5 out of 6 DES. Antagonism was observed for [N1111]Cl-based DES, and synergism for [N3333]Cl-based DES and for 1-propanol:[N2222]Cl. The application of the mixture toxicity models represents a breakthrough in the problematic of assessing the toxicity of the countless number of DES that can be created with the same starting materials, since they provide the expected toxicity of any virtual combination between HBA and HBD.
Highlights
Over the past decades, the design of environmentally friendlier solvents has gained increased attention, driven by global awareness of environmental pollution
In this study we consider the deep eutectic solvents (DES) aqueous solutions as a mixture, and aimed to evaluate the applicability of the mixture theory models to the understanding and prediction of the toxicity of DES based on non conventional hydrogen bond acceptors (HBA)
The cell wall in gram negative bacteria such as A. fischeri possesses molecules of peptidoglycan outside of the cytoplasmatic membrane, which are responsible for the rigidity and strength of the structure (Nelson and Cox, 2012)
Summary
The design of environmentally friendlier solvents has gained increased attention, driven by global awareness of environmental pollution. The DES tailor-made character makes them appealing for several applications within chemistry (Radosevic et al, 2015), and pharmaceutical/biomedical (Mbous et al, 2017a) fields. Following their production and use, they can reach aquatic systems, causing toxicity to aquatic biota, the recent interest on the toxicity profile of DES. Following their production and use, they can reach aquatic systems, causing toxicity to aquatic biota, the recent interest on the toxicity profile of DES. (Eco)toxicity of several [Chol]Cl and phosphoniumbased DES was assessed through a variety of organisms (Cardellini et al, 2015; de Morais et al, 2015; Hayyan et al, 2015, 2013a; 2013b; Huang et al, 2014; Juneidi et al, 2016; Radosevic et al, 2015; Wen et al, 2015; Zhao et al, 2015), as well as through several cell lines (Hayyan et al, 2016, 2015; Mbous et al, 2017b; Paiva et al, 2014; Radosevic et al, 2015)
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