Unraveling the ecotoxicity of deep eutectic solvents using the mixture toxicity theory

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 [N-1111]Cl, [N-2222]Cl and [N-3333]Cl as hydrogen bond acceptors (HBA) combined with hydrogen-bond donors (HBD) vis. ethylene glycol and 1-propanol, through the Microtox (R) 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 [N-3333]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: [N-1111]Cl-based DES < [N-2222]Cl-based DES < [N-3333]Cl-based DES. The IA model, with specific deviations, adjusted better in 5 out of 6 DES. Antagonism was observed for [N-1111]Cl-based DES, and synergism for [N3333]Cl-based DES and for 1-propanol:[N-2222]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. (C) 2018 Elsevier Ltd. All rights reserved.

keywords

CHEMICAL-MIXTURES; IONIC LIQUIDS; WATER; BIODEGRADABILITY; CYTOTOXICITY; EXTRACTION

subject category

Environmental Sciences & Ecology

authors

Macario, IPE; Jesus, F; Pereira, JL; Ventura, SPM; Goncalves, AMM; Coutinho, JAP; Goncalves, FJM

Groups

G4 - Renewable Materials and Circular Economy

Projects

CICECO - Aveiro Institute of Materials (UID/CTM/50011/2013)

ToxMix - Toxicity of mixtures of alternative solvents with industrial potential (PTDC/ATP-EAM/5331/2014)

Projeto de Investigação Exploratória: Sónia Patricia Marques Ventura (IF/00402/2015)

acknowledgements

Thanks are due for the financial support to CESAM - Centre for Environmental and Marine Studies, University of Aveiro, Portugal (UID/AMB/50017 - POCI-01-0145-FEDER-007638), to FCT - Portuguese Foundation for Science and Technology/MCTES - Ministry of Science, Technology and Higher Education, Portugal through national funds (PIDDAC), and the co-funding by the FEDER, within the PT2020 Partnership Agreement and Compete 2020. This work was also developed within the scope of the project CICECO-Aveiro Institute of Materials, University of Aveiro, Portugal, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC - Ministry of Education and Science, Portugal and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. The authors also acknowledge the support by the FCT through the project PTDC/ATP-EAM/5331/2014, the doctoral grant of IPE Macario (SFRH/BD/123850/2016) and post-doctoral grants of AMM Goncalves and JL Pereira (SFRH/BPD/97210/2013, SFRH/BPD/101971/2014), respectively. SPM Ventura acknowledges FCT for the contract IF/00402/2015. We are also grateful to Prof. Antonio JA Nogueira for giving us permission to use the ToxCalcMix spreadsheet.