engleski

"SPE-MASE" Coupled System for Extraction of Pesticides from Water Samples

Solid-phase extraction (SPE) procedure is a technique commonly used for preconcentration of pesticides from water samples [1] whereas microwave assisted solvent extraction (MASE) technique is extraction procedure, which is used for preconcentration of different compounds from soil samples and sediments. While SPE prefers usage of non-polar solvent (hexane or dichloromethane) in case when non-polar sorbent like C18 modified silica-gel is used, MASE needs polar solution as appropriate solvent. In combination with SPE, MASE is capable of preconcentrating this compound from water samples, too. The aim of this investigation was efficiency improvement of atrazine, alachlor and alpha-cypermethrin pesticides extraction from spiked water samples applying SPE followed by microwave assisted solvent extraction (MASE). In this way, MASE serves for elution of pesticides from C18-extraction discs with solvent heated by microwave energy. In comparison to conventional SPE the benefits of the combination applied are low solvent consumption, use of polar solvent with non-polar sorbent (ethanol as less toxic solvent then hexane or dichloromethane is used as polar solvent for MASE), better extraction efficiency and reduction of extraction time, as 12 samples are extracted at the same time. Extraction efficiency was determined by thin-layer chromatography using 2- propanol:water = 8:2 as developer on HPTLC RP-18 F254s plates. Experimental parameters such as volume of solvent (mL), temperature (°C) and duration of elution (minute) affect the extraction efficiency of SPE-MASE coupled system and needs to be optimized for selected pesticides. In order to develop mathematical model, 15 experiments in central composite design were performed. This equation was then used to predict the recoveries of pesticides at certain experimental conditions. Optimization of microwave extraction was accomplished using genetic algorithm approach. The best results were achieved using 20 mL of ethanol at 60°C. Optimal holding time was 5 minutes and 48 sec.

solid-phase extraction (SPE); microwave-assisted solvent extraction (MASE); pesticides; wWater; thin-layer chromatography (TLC)

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