title: Dissipation behaviour, processing factors and risk assessment for metalaxyl in greenhouse-grown cucumber.
abstract: BACKGROUND
  Cucumber is widely cultivated in Iran, and the application of systemic and protective fungicides is the main choice of disease treatment, particularly in greenhouse-grown systems. In this research, cucumber fruits were harvested at 1 h to 25 days after the last application to determine the residue and dissipation behaviour of metalaxyl. The effects of peeling and storage (at 3 °C for 4 days) on metalaxyl residue reduction were also assessed. Samples were extracted by the QuEChERS procedure then analysed using liquid chromatography-tandem mass spectrometry.
  
  
  RESULTS
  The dissipation of metalaxyl residues approximately fitted a first-order kinetic model, obtaining half-life values of 2.2 and 3.8 days and preharvest interval values of 5.2 and 12.5 days at the recommended dose (2 kg ha(-1) ) and double (4 kg ha(-1) ) dose respectively. The processing factor values for peeling and storage were 0.50 and 0.93 respectively, showing that storage had little effect on residue reduction compared with peeling.
  
  
  CONCLUSIONS
  The higher content of metalaxyl residues in flesh showed its penetration from the skin into the flesh. The results provided more understanding of fungicide distribution as well as the effective role of peeling in reducing residues in cucumber fruits.
authors.affiliation: Pesticide Research Department, Iranian Research Institute of Plant Protection, Tehran, Iran.
authors.forename: Mohammad Kazem
authors.initials: MK
authors.lastname: Ramezani
authors.forename: Dariush
authors.initials: D
authors.lastname: Shahriari
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000032:analysis; D002853:Chromatography, Liquid; D018553:Cucumis sativus / Q000737:chemistry*; D004784:Environmental Monitoring; D005638:Fruit / Q000737:chemistry; D005659:Fungicides, Industrial / Q000032:analysis*; D006207:Half-Life; D006801:Humans; D007492:Iran; D007700:Kinetics; D010573:Pesticide Residues / Q000032:analysis*; D018570:Risk Assessment; D012989:Soil Pollutants / Q000032:analysis; D053719:Tandem Mass Spectrometry
chemical_list: D005659:Fungicides, Industrial; D010573:Pesticide Residues; D012989:Soil Pollutants; C028175:metalaxyl; D000409:Alanine
keywords: cucumber; dissipation; half-life; liquid chromatography-tandem mass spectrometry; metalaxyl; risk assessment