Abstract
A fast method based on Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) modified QuEChERS integrated to dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry was established for the determination of 8 organochlorine pesticides (OCPs) in green leafy vegetables. The factors involved in the purification by QuEChERS and concentration by DLLME were optimized. In the QuEChERS process, Fe3O4 MNPs were used as a new impurity adsorbent after the sample extraction procedure by acetonitrile, which achieved phase separation rapidly. Carbon black was used as an alternative to costly graphitized carbon black without affecting the recovery. In the process of DLLME, 1 mL of the extract obtained by QuEChERS was used as the dispersive solvent, 40 μL of chloroform was used as the extractive solvent, and 4 mL of water was added. Making them mix well, then the dispersed liquid-liquid microextraction concentration was subsequently carried out. The enrichment factors of 8 OCPs ranged from 22.8 to 36.6. The recoveries of the proposed method ranged from 78.6% to 107.7%, and the relative standard deviations were not more than 7.5%. The limits of detection and limits of quantification were 0.15–0.32 μg/kg and 0.45–0.96 μg/kg, respectively. The method has been successfully applied to the determination of OCPs in green leafy vegetable samples.
Highlights
Green leafy vegetables can provide essential nutrients such as vitamins, dietary fiber, and minerals, which have been deemed as essential in people’s daily life
Acetone, and ACN endowed excellent miscibility in both extraction solvent and aqueous phase. They were used as an extraction solvent in this study. e results showed that when methanol was used as the extraction agent, the solution was not stratified after adding NaCl, and the organic phase could not be obtained; the follow-up experiments cannot be carried out smoothly
ACN has stronger selectivity to Organochlorine pesticides (OCPs) and the organic phase can be separated from water quickly through salting out. erefore, ACN was chosen as a suitable extraction agent
Summary
Green leafy vegetables can provide essential nutrients such as vitamins, dietary fiber, and minerals, which have been deemed as essential in people’s daily life. Gas chromatography-mass spectrometry (GC-MS) exhibits excellent selectivity and sensitivity It adopts full SCAN mode for qualitative analysis and selected ion monitor (SIM) mode for quantitative analysis, which is widely used in the detection of low-concentration organic compounds. Researchers have developed fast, sensitive, and environmentally friendly pretreatment methods to separate and enrich pesticide residues in different matrixes such as solid-phase microextraction (SPME) [17], gel permeation chromatography (GPC) [18], QuEChERS [19], and DLLME [20]. The traditional QuEChERS technology still requires multistep centrifugation separation, which seriously affects the pretreatment speed of batch samples and has the disadvantages of low enrichment multiple and high detection limit. Fe3O4 MNPs modified QuEChERS integrated to DLLME coupled with GC-MS was used to determine 8 OCPs in green leafy vegetables. Systematical optimization was studied in detail during the various influencing factors of QuEChERS and DLLME. e method is simple, fast, safe, and cheap with good repeatability. is may be the first report about the application of Fe3O4 MNPs-QuEChERS-DLLME-GC-MS for the analysis of pesticides in real samples
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