Ionic-liquid-modified magnetite nanoparticles for MSPE-GC-MS determination of 2,4-D butyl ester and its metabolites in water, soil, and bottom sediments

Abstract

Efficient sorbents based on magnetite nanoparticles and ionic liquids are proposed for solid-phase extraction of the pesticide, butyl 2,4-dichlorophenoxyacetate (2,4-DB), and its metabolites, 2,4-dichlorophenoxyacetic acid (2,4-D), 2,4-dichlorophenol (2,4-DCP), and 4-chlorophenol (4-CP). Fe3O4 nanoparticles were modified with 1-carboxymethyl-3-methylimidazolium chloride, 1,3-dimethylimidazolium-2-carboxylate, and 1,3-dimethylimidazolium-2-carboxylate. The obtained sorbents possess a saturation magnetization of 29–37 emu/g and a specific surface area of 89.7–119.5 m2g−1. The highest extraction efficiency was achieved for the sorbent modified with 1,3-dimethylimidazolium-2-carboxylate. Upon single extraction (the sorbent weight was 0.02 g, pH 4–5, t = 20 min), 98–99% of 2,4-D and 2,4-DB, 92% of 2,4-DCP, and 94% of 4-CP were extracted. The enrichment factor after desorption reached 1602–1710. The limit equilibrium sorption was 303.1–520.8 mg g−1.The combination of MSPE with GC-MS was used to monitor the pollution of soils, ground and river waters, and bottom sediments by 2,4-DB and its metabolites. Also, the distribution of the pesticide and its metabolites over the profile of typical and residual-calcareous chernozems up to a depth of 110 cm was studied. The limits of detection of 2,4-D and 2,4-DB were 0.1 ngL−1 upon determination in distilled water, 0.5–0.6 ngL−1 in river and ground waters, 10 ng kg−1 in soil, and 25–30 ng kg−1 in bottom sediments. The limits of detection of 4-CP and 2,4-DCP were slightly lower to be 5 ngL−1 in distilled water and 8–10 ngL−1 in river and ground waters. Upon determination in complex matrices, such as soils, the limits of detection of 4-CP and 2,4-DCP were 10–15 ng kg−1.