Discovering less toxic ionic liquids by chlorophyll fluorescence measurements assays of the microalgae Pseudokirchneriellasubcapitata

Resumen

Ionic liquids (ILs) are organic salts that remain liquid near room temperature. They consist of an organic cation andpolyatomic inorganic or organic anion. Examples of cations are imidazolium, pyridinium, pyrrolidinium,phosphonium, ammonium, and anions are tetrafluoroborate, hexafluorophosphate, chloride,trifluoromethylsulfonate, and bis[(trifluoromethyl)sulfonyl]imide). Microbial fuel cells (MFCs) are bioelectrochemicalreactor in which organic substrates are oxidized by microorganism and electricity is simultaneous produced.Membranes based on ionic liquids were used in the last generation of MFCs. Some research lines on MFC try tointegrate microalgae on the cathode in order to produce oxygen, which is needed by the cathode reaction, and alsoproduced microalgae biomass. For those newintegrate systems the used of biocompatible ionic liquid on microalgaeis essential [1].Chlorophyll fluorescence analyses are new method that has been used to study the photosynthetic toxicity and otherpollutants on algae in recent years [2]. Chlorophyll fluorescence analyses are based on the photosynthetic theory,using chlorophyll fluorescence in vivo as a probe to study the photosynthetic physiological state of organisms underthe influences of various external factors. Chlorophyll fluorescence analysis is rapid and sensitive, and it can alsodetect the photosynthetic toxicity with no damage to algae.Until now, chlorophyll fluorescence assays of microalgae have been used for determining the toxicity of organic andmetal ions pollutant to microalgae. In this work, for the first time, the toxic effects of 21 ionic liquids on the greenalgae Pseudokirchneriellasubcapitatawere studied by chlorophyll fluorescence analysis by using a Junior-PAMfluorometer (Walz-Germany). The different anion and cation composition allow us to analyze the effect of the ionicliquid composition and establish qualitative structure–properties relationships in order to designing ionic liquids withless ecotoxicological risk than conventional organic solvents.It is worthy to highlightthat some of the ionic liquids tested result to be biocompatible at low concentration such us1-ethyl-1-methyl pyrrolidinium bis[(trifluoromethyl)sulfonyl] imide, (poly[oxy(methyl-1,2-ethanediyl)]-a-[2-diethylmethylammoniumetyl]-w-hydroxy chloride, choline dihydrogen phosphate, etraoctylphosphonium bromideand tributyl(tetradecyl)phosphonium dodecylbenzene sulfonate.