| Abstract |
Esters are organic compounds that are widespread and can be obtained naturally or chemically. Fatty acid esters of polyethylene glycols (PEG) are particularly attractive due to their low toxicity, lack of immunogenicity, antigenicity and solubility in water and organic solvents. They are used in industrial, medicinal, and cosmetic applications as detergents, lubricants, wetting agents, solubilizers, and emulsifiers.The most commonly used method of synthesizing esters is the Fisher esterification reaction. Fatty acids (caprylic, lauric, and palmitic) were reacted with polyethylene glycol (PEG 400 and PEG 600) to synthesize non-ionic surfactants, then they were elucidated by IR spectrum and mass spectrometry, and then their physico-chemical properties were estimated such as HLB, CMC, free acidity or alkalinity, as well as solubility in various solvents. Physico-chemical characteristics of pesticide spray solution were estimated separately before and after mixing with esters. After that, the 4th instar larvae of the cotton leaf-worm and the greater wax worm were treated with serial concentrations of the recommended pesticide and treated by LC50 of the pesticide with esters. Results showed that, the synthesized esters were successful in enhancing the physico-chemical properties of spray solutions. As a result of mixing pesticide with surfactants, pesticides' viscosity and conductivity increased while their surface tension and pH value decreased. Furthermore, the results of the bioassay test showed that all surfactants reduced the LC50 value of the insecticides (Emamectine benzoate 1.9% EC and Pyrethrum 5% EC). Thus, it is recommended to combine these esters with pesticide spray solutions in order to decrease the amount of pesticide utilized and subsequently contamination of the environment. |
