محبوبه شیرانی

Background: Pyrethroids have been increasingly used to replace organophosphate pesticides which are widely banned due to their highly toxic and persistent nature [1]. Pyrethroid insecticides disrupt the sodium channel which leads to the death of a variety of insects. Permethrin and deltamethrin are two potent and common pyrethroids which are extremely toxic to aquatic life, bees, and wildlife. Therefore, separation/preconcentration of trace amount of permethrin and deltamethrin is essential. Solidification of floating organic drop liquid-phase microextraction (SFO-LPME) based on dispersive liquid–liquid microextraction (DLLME) is a facile and efficient method in which the extraction solvent is solidified near room temperature and can be easily separated without centrifugation [2]. Methods: In the present study, 5 mL aqueous sample of water free from pesticides was placed in a 10 mL falcon test tube and spiked with the target analytes 50 ng L-1. Acetonitrile (0.5 mL) as disperser solvent and 30 µL 1-undecanol as extraction solvent was rapidly injected into the sample solution with a 1mL syringe. A cloudy solution, resulting from the dispersion of fine droplets in the aqueous solution, was formed in the test tube. After centrifugation for 5 min at 4000 rpm, the falcon tube was transferred into a beaker containing crushed ice; the organic solvent was solidified in 5 min. After 5 min, the solidified solvent was transferred to a conical vial; it melted quickly at room temperature and 1µL of 1-undecanol containing permethrin and delthametrin was injected to GC-MS. Results: Dispersive liquid–liquid microextraction based on solidification of floating organic drop coupled with gas chromatography-mass spectrometry was applied for separation/preconcentration and determination of permethrine and deltamethrin. The detection limits of 5 ng L-1 and 3 ng L-1 for permethrin and delthametrin respectively, the linear ranges of 10-250 ng L-1 were achieved for both analytes. The precisi