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Designing ionic liquids: the chemical structure role in the toxicity

Ecotoxicology volume 22, pages 1–12 (2013)Cite this article

Abstract

Ionic liquids (ILs) are a novel class of solvents with interesting physicochemical properties. Many different applications have been reported for ILs as alternatives to organic solvents in chemical and bioprocesses. Despite the argued advantage of having low vapor pressure, even the most hydrophobic ILs show some degree of solubility in water, allowing their dispersion into aquatic systems and raising concerns on its pollutant potential. Moreover, nowadays most widespread notion concerning the ILs toxicity is that there is a direct relationship with their hydrophobicity/lipophilicity. This work aims at enlarging the currently limited knowledge on ILs toxicity by addressing negative impacts in aquatic ecosystems and investigating the possibility of designing hydrophobic ILs of low ecotoxicity, by the manipulation of their chemical structures. The impact of aromaticity on the toxicity of different cations (pyridinium, piperidinium, pyrrolidinium and imidazolium) and hydrophobic anions (bis(trifluoromethylsulfonyl)imide [NTf2] and hexafluorophosphate [PF6]) was analysed. Concomitantly, several imidazolium-based ILs of the type [C n C m C j im][NTf2] were also studied to evaluate the effects of the position of the alkyl chain on the ILs’ toxicity. For that purpose, standard assays were performed using organisms of different trophic levels, Vibrio fischeri, Pseudokirchneriella subcapitata and Daphnia magna, allowing to evaluate the consistency of the structure–activity relationships across different biological targets. The results here reported suggest the possibility of designing ILs with an enhanced hydrophobic character and lower toxicity, by elimination of their aromatic nature.

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Acknowledgments

The authors are grateful for financial support from FEDER funds through the Program COMPETE and by National Fund through the Portuguese Foundation for Science and Technology (FCT) under the scope of the Projects Pest-C/CTM/LA0011/2011 and PTDC/AAC-AMB/119172/2010. The authors also thank financial support through the Post-doctoral Grants SFRH/BPD/79263/2011 and SFRH/BPD/44733/2008 of S. P. M. Ventura and J. L. Pereira, respectively.

Conflict of interest

The authors declare that they have no conflict of interest.

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Authors and Affiliations

  1. Departamento de Química, CICECO, Universidade de Aveiro, Campus Universitário de Santiago, 3810-193, Aveiro, Portugal

    Sónia P. M. Ventura, Tânia Sintra & João A. P. Coutinho

  2. Departamento de Biologia & CESAM (Centro de Estudos do Ambiente e do Mar), Universidade de Aveiro, 3810-193, Aveiro, Portugal

    Ana M. M. Gonçalves, Joana L. Pereira & Fernando Gonçalves

  3. Departamento das Ciências da Vida, Faculdade de Ciências e Tecnologia, IMAR-CMA (Instituto do Mar), Universidade de Coimbra, 3004-517, Coimbra, Portugal

    Ana M. M. Gonçalves

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  1. Sónia P. M. Ventura
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  2. Ana M. M. Gonçalves
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  3. Tânia Sintra
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Correspondence to João A. P. Coutinho.

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Ventura, S.P.M., Gonçalves, A.M.M., Sintra, T. et al. Designing ionic liquids: the chemical structure role in the toxicity. Ecotoxicology 22, 1–12 (2013). https://doi.org/10.1007/s10646-012-0997-x

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Keywords

  • Ionic liquids
  • Toxicological tests
  • Aquatic toxicity
  • EC50
  • Aromatic/aliphatic nature
  • Isomerism