Preconcentration and determination of carbaryl and carbofuran in water samples using ionic liquids and in situsolvent formation microextraction

Abstract

In the present work, a novel microextraction method named in situ solvent formation microextraction (ISFME) using ionic liquids (ILs) for preconcentration of carbaryl and carbofuran in water samples is introduced. In this method, a small amount of sodium hexafluorophosphate (NaPF₆), as an ion pairing agent, was added to a sample solution containing a small quantity of 1-hexyl-3-methylimidazolium tetrafluoroborate [Hmim][BF₄] as a hydrophobic ionic liquid. A cloudy solution formed as a result of formation of fine droplets of 1-hexyl-3-methylimidazolium hexafluorophosphate [Hmim][PF₆]. After centrifugation, the fine droplets of the extractant phase settled to the bottom of the conical-bottom glass centrifuge tube. Analysis was carried out using HPLC-UV. To obtain the best extraction results, some experimental parameters affecting the extraction efficiency were optimized. Under optimum conditions, the calibration curve was linear in the concentration range of 0.05–50 ng mL⁻¹ for two pesticides, with the square correlation coefficients (r²) equal to 0.998 for carbaryl and 0.997 for carbofuran. Good enrichment factors of 85 and 100 were achieved for carbaryl and carbofuran, respectively. The limits of detection (LODs) (S/N = 3) were 0.09 ng mL⁻¹ and 0.1 ng mL⁻¹ for carbaryl and carbofuran, respectively. The method was successfully applied to analysis of pesticide residues in water samples.