Assessing the mutagenicity of protic ionic liquids using the mini Ames test

Abstract

Protic ionic liquids (PILs) have been suggested as “greener” alternatives to conventional solvents in various industrial applications. In order to assess their suitability for such purposes, a thorough evaluation of their toxicity, mutagenicity, carcinogenicity and environmental impact is crucial. Whilst some studies have been published concerning the biodegradability and toxicity towards microorganisms of a limited number of PILs, no data concerning the mutagenicity of any PIL exist within the literature. As part of our ongoing studies into the toxicity and environmental impact of PILs, we quantify herein the mutagenic potential of a range of PILs through the mini Ames test. In total, 16 PILs and two precursor amines were assessed based on the Ames test, using Salmonella typhimurium strains TA98 and TA100. The 16 PILs used in this study included both carboxylate and chloride anions, as well as secondary and tertiary ammonium cations. Our results show that out of the 16 PILs, 15 gave negative results to the mini Ames test, concluding that they are unlikely to be either mutagenic or carcinogenic. The PIL N,N-Dimethylethanolammonium Octanoate ([DMEtA][Oct]) was toxic to both test strains, and its mutagenic potential could not be assessed by the mini Ames test. The two precursor amines, diethanolamine and N,N-dimethylethanolamine, gave negative results to the mini Ames tests despite the suggestion from other mutagenicity tests of diethanolamine’s suggested carcinogenicity. 15 PILs have been deemed likely to be neither mutagenic nor carcinogenic in accordance with the mini Ames test. We find that these results compare well to the relevant carboxylic acids and amines from the literature, suggesting that PILs exist as well solvated ions in these test conditions, similar to those of their precursors in the same test. From this, we caution the use of secondary ammonium cations in PILs, as certain secondary amines have been suggested to be potentially carcinogenic, despite their results from the mini Ames test.