engleski

Optimization of microwave assisted solvent extraction by using genetic algorithm

For the isolation of pesticides from sediment and soil samples various extraction and clean-up procedure have been proposed. Almost all traditional methods (shake-flask, Soxhlet, ...) are time and solvent consuming. Due to the long extraction process, degradation of the components can occur. In comparasion to conventional extraction procedures the benefits of microwave extraction are enhanced extraction times, low solvent consumption and improved extraction efficiencies. Moreover simultaneous extraction of up to 12 samples is possible. After a comercial closed vessel temperature and pressure controled microwave instrument become available, microwave extraction was more attractive for organic compounds. The aim of this work is to optimise microwave solvent extraction of pesticides atrazine and simazine from sediment and soil samples. The extracted pesticides were identified and quantified using TLC-denitometry. The recovery of pesticides was determined by quantitative thin layer chromatography on silicagel plates with hexan:chloroform:acetone (60:25:15, v/v/v). The chromatograms were recorded with CAMAG Video Documentation System in conjuction with the Reprostar 3. The chromatograms were captured under UV light (254 nm) by means of 3CCD color video camera HV-C20. The efficiency of microwave extraction of selected samples was examined on spiked samples with various solvents (ethanol, acetone, chloroform, acetonitrile, dichlormetane, ethyl acetate, methanol, diethyl ether). Optimization of microwave extraction of pesticides from soil samples was accompliched using a genetic algorithm approach. Genetic algothms (GAs) are probabilistic search procedures. They search for global minimum or maximum of a function. The principles of genetic algorithms are based on population that represents a set of possible solutions of the problem examined. The members of the population are called chromosomes, as in the natural evolution. Every chromosome is composed of units called genes. Each gene is a parameter of the proposed model. The extraction was optimised regarding the solvent amount, the duration of microwave extraction and the temperature. Microwave assisted solvent extraction using ethanol showed satisfactory extraction efficiencies combined with low solvent and time consumption.

microwave solvent extraction; pesticides; sediment; soil; optimization; genetic algorithm

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