Two-step microextraction combined with high performance liquid chromatographic analysis of pyrethroids in water and vegetable samples

Dispersive liquid microextraction (DLME) combined with dispersive µ-solid phase extraction (D-µ-SPE) has been developed as a new approach for the extraction of four pyrethroids (tetramethrin, fenpropathrin, deltamethrin and permethrin) prior to the analysis by high performance liquid chromatography (HPLC) with UV detection. 1-Octanol was used as the extraction solvent in DLME. Magnetic nanoparticles (Fe3O4) functionalized with 3-aminopropyl triethoxysilane (APTS) were used as the dispersive in DLME and as the adsorbent in D-µ-SPE. The extracted pyrethroids were separated within 30 min using isocratic elution with acetonitrile:water (72:28). The factors affecting the extraction efficiency were investigated. Under the optimum conditions, the enrichment factors were in the range of 51–108. Linearity was obtained in the range 0.5–400 ng mL−1 (tetramethrin) and 5–400 ng mL−1 (fenpropathrin, deltamethrin and permethrin) with the correlation coefficients (R2) greater than 0.995. Detection limits were 0.05–2 ng mL−1 (water samples) and 0.02–2.0 ng g−1 (vegetable samples). The relative standard deviations of peak area varied from 1.8 to 2.5% (n=10). The extraction recoveries of the four pyrethroids in field water and vegetable samples were 91.7–104.5%. The proposed method has high potential for use as a sensitive method for determination of pyrethroid residues in water and vegetable samples.