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Toxicity to aquatic algae and cyanobacteria

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Description of key information

1-ETHYL-3-METHYL IMIDAZOLIUM ETHYLSULFATE inhibited cell growth of Selenastrum capricornutum significantly (29%) at nominally 100 mg/L. However, no reduction of growth rate was recorded at any of the concentrations of EMIM ES tested. The EC50 for cell growth inhibition (EbC50: 0-72h) was beyond 100 mg/L based on analytically confirmed nominal concentrations.
As growth rate is derived from the slope under the growth curve in a logarithmic plot, the measurement of the specific growth rate is preferable over biomass following from the mathematical nature of exponential growth.
The EC50 for growth rate reduction (ErC50: 0-72h) was beyond 100 mg/L based on analytically confirmed nominal concentrations.
The NOEC for cell growth inhibition was < 100 mg/L. The NOEC for growth rate reduction was 100 mg/L.

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Additional information

Selenastrum capricornutum, Fresh Water Algal Growth Inhibition Test with l-ETHYL-3-METHYL IMIDAZOLIUM ETHYLSULFATE.

The study procedures described in this report were based on the ISO International Standard 8692, 1989. In addition, the procedures were designed to meet the test methods and validity criteria of the EEC directive 92/69, Part C.3, 1992, the OECD guideline No. 201, 1984 and the OECD series on testing and assessment number 23, 2000.

The batch of 1-ETHYL-3-METHYL IMIDAZOLIUM ETHYLSULFATE tested was a light yellow viscous liquid with a purity of 99.0% and completely soluble in test medium at the concentrations tested. Preparation of test solutions started with a stock solution of 100 mg/L applying 17 minutes of magnetic stirring to accelerate the dissolving of the test substance in the test medium. The lower test concentrations were prepared by subsequent dilutions of the stock in test medium. The final test solutions were all clear and colourless.

A combined limit/range-finding test was performed, exposing six replicates of exponentially growing algal cultures to a nominal 1-ETHYL-3-METHYL IMIDAZOLIUM ETHYLSULFATE concentration of 100 mg/L and a blank-control. In addition three replicates of exponentially growing algal cultures were exposed to nominal 1-ETHYL-3-METHYL IMIDAZOLIUM ETHYLSULFATE concentrations of 0.1, 1.0 and 10 mg/L. The total test period was 72 hours and samples for analytical confirmation of actual test concentrations were taken from the blankcontrol and the 100 mg/L concentration at the start and the end of the test period. Analysis of the samples taken at the start of the combined limit/range-finding test showed that the mean actual test concentration was in agreement with nominal (86%) and remained stable during the 72-hour test period (i.e. 102% of initial). Based on these results, the NOEC and the EC50 were based on nominal concentrations. The study met the acceptability criteria prescribed by the protocol and was considered valid.

1-ETHYL-3-METHYL IMIDAZOLIUM ETHYLSULFATE inhibited cell growth of Selenastrum capricornutum significantly (29%) at nominally 100 mg/L. However, no reduction of growth rate was recorded at any of the concentrations of EMIM ES tested. The EC50 for cell growth inhibition (EbC50: 0-72h) was beyond 100 mg/L based on analytically confirmed nominal concentrations.

As growth rate is derived from the slope under the growth curve in a logarithmic plot, the measure of the specific growth rate is preferable over biomass following from the mathematical nature of exponential growth.

The EC50 for growth rate reduction (ErC50: 0-72h) was beyond 100 mg/L based on analytically confirmed nominal concentrations.

The NOEC for cell growth inhibition was < 100 mg/L. The NOEC for growth rate reduction was 100 mg/L.