RESUMEN
A modified QuEChERS-GC-MS method for analysis of procymidone residue in leeks and soil was developed and validated. Procymidone residue dynamics and residues in supervised field trials at GAP conditions in leeks and soil in greenhouses were studied. Leek samples were treated under microwave radiation for 1min before homogenization, followed by extracting with acetonitrile and clean-up with reverse solid phase dispersion by primary and secondary amine (PSA). Procymidone residue was determined by GC-MS in selected ion monitoring (SIM) mode. At fortification levels of 0.02, 0.2 and 2mg/kg in leeks and soil, it was shown that recoveries ranged from 74.9% to 100.8% with relative standard deviations of 1.3-8.5%. At four geographical experimental plots, procymidone residue in leeks and soil showed a relatively fast dissipation rate, with half-lives of 4.52-8.76 days for leeks and 3.76-5.65 days for soil. At pre-harvest intervals of 21-30 days, procymidone residue ranged from 0.033 to 0.17mg/kg in leeks, and 0.020-1.75mg/kg in soil. Residues persistence varied in leeks and soil in four field trials, suggesting that it might be affected by some physical and chemical factors, growth dilution factor, soil characteristics and microorganisms.