Toxicity evaluation of selected ammonium-based ionic liquid forms with MCPP and dicamba moieties on Pseudomonas...

Area of Science:

• Environmental chemistry
• Toxicology
• Green chemistry

Background:

• Ionic liquids (ILs) offer improved properties over conventional herbicides.
• Modifying cation/anion structures, including alkyl chain length, affects IL properties.
• Limited data exists on the toxicity of herbicidal ILs and the hydrophobicity-toxicity relationship.

Purpose of the Study:

• Investigate the toxicity of herbicidal ionic liquids on the soil bacterium Pseudomonas putida.
• Determine the relationship between alkyl chain length in quaternary ammonium salts and toxicity.
• Assess cis-trans isomerization of fatty acids as a toxicity and membrane activity indicator.

Main Methods:

• Synthesized herbicidal ILs with dicamba or MCPP anions and quaternary ammonium cations of varying alkyl chain lengths (C6, C8, C10).
• Determined growth inhibition (EC50) of Pseudomonas putida.
• Compared IL toxicity to commercial herbicides and neutral anion ILs.
• Analyzed cis-trans isomerization of unsaturated fatty acids in bacterial membranes.

Main Results:

• Toxicity generally increased with alkyl chain length, but this trend plateaued for C10 chains.
• Herbicidal ILs [C10,C10,C1,C1N][MCPP] and [C10,C10,C1,C1N][dicamba] showed the lowest toxicity.
• Toxicity of these ILs was comparable to their respective commercial herbicide forms.
• No significant toxicity increase was observed with anion modification in ammonium-based ILs.

Conclusions:

• Alkyl chain length is a critical factor in herbicidal IL toxicity, with an optimal range for reduced toxicity.
• Specific IL structures demonstrate potential as safer alternatives to conventional herbicides.
• Further research into structure-toxicity relationships is crucial for developing environmentally benign agrochemicals.