Magnetic solid-phase extraction or dispersive liquid-liquid microextraction for pyrethroid determination in environmental samples.

The determination of 15 pyrethroids in soil and water samples was carried out by gas chromatography with mass spectrometry. Compounds were extracted from the soil samples (4 g) using solid-liquid extraction and then salting-out assisted liquid-liquid extraction. The acetonitrile phase obtained (0.8 mL) was used as a dispersant solvent, to which 75 μL of chloroform was added as an extractant solvent, submitting the mixture to dispersive liquid-liquid microextraction. For the analysis of water samples (40 mL), magnetic solid-phase extraction was performed using nanocomposites of magnetic nanoparticles and multiwalled carbon nanotubes as sorbent material (10 mg). The mixture was shaken for 45 min at room temperature before separation with a magnet and desorption with 3 mL of acetone using ultrasounds for 5 min. The solvent was evaporated and reconstituted with 100 μL acetonitrile before injection. Matrix-matched calibration is recommended for quantification of soil samples, while water samples can be quantified by standards calibration. The limits of detection were in the range of 0.03-0.5 ng/g (soil) and 0.09-0.24 ng/mL (water), depending on the analyte. The analyzed environmental samples did not contain the studied pyrethroids, at least above the corresponding limits of detection.