Thiacloprid Residues in Green Onion (Allium cepa) Using Micro Liquid–Liquid Extraction and Liquid Chromatography–Tandem Mass Spectrometry
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Conventional sample preparation methods for liquid chromatography–mass spectrometry (LC–MS/MS) are time consuming, laborious, expensive, and require large volumes of solvent for extraction and cleanup. We developed and validated a micro liquid–liquid extraction (MLLE) sample preparation method for LC–MS/MS analysis of thiacloprid insecticide residues in green onion. MLLE is a simple, rapid, and cost-effective method that uses less extraction solvent and does not require adsorbents or the cleanup step. The samples are homogenized with dichloromethane, centrifuged, the solvent evaporated to dryness and the residue is reconstituted with fivefold of acetonitrile; thus, the method is ecologically safer and low cost. The limit of quantification was 0.01 mg/kg. Method efficiency for MLLE was compared with the conventional QuEChERS sample preparation. MLLE exhibited good linearity (correlation coefficient, > 0.99). The average recovery ranged from 97.2 to 101.5%. Intra- and inter-day repeatabilities were 9.7 and 13.8%, respectively. Matrix effects were nonsignificant (suppression, 2.2%). The MLLE method was used to quantify the residual levels and rate of dissipation of thiacloprid in field trial green onion. The dissipation of thiacloprid fitted first-order kinetics, with half-lives of 1.92 and 2 days after application of the recommended dose (48 g a.i/ha) and double the recommended dose (96 g a.i/ha). Thiacloprid residues were below the limit of detection in green onion samples analyzed 14 days after spraying with either dose. Based on the maximum residue limit, a waiting period of 9 days is recommended. From Egyptian consumers’ point of view, the consumption of onion seems quite safe.
KeywordsThiacloprid Residue distribution QuEChERS Micro liquid–liquid extraction Green onion Risk assessment
Osama I. Abdallah and Farag M. Malhat contributed to the conception and design of the experiment, analysis of samples, and data analysis. Farag M. Malhat did the sample collection. Osama I. Abdallah wrote the manuscript.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest.
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