title: Analysis of imidacloprid and pyrimethanil in shallot (Allium ascalonicum) grown under greenhouse conditions using tandem mass spectrometry: establishment of pre-harvest residue limits.
abstract: In this study, the original Quick, Easy, Cheap, Effective, Rugged and Safe method was used for the extraction of imidacloprid and pyrimethanil followed by a rapid clean-up through dispersive solid-phase extraction technique with primary secondary amine sorbent and magnesium sulfate in shallot. Residues were analyzed using LC-tandem mass spectrometry in positive-ion electrospray ionization mode. The limits of detection and quantification were estimated to be 0.006 and 0.02 mg/kg, respectively. The samples were fortified at two different concentration levels (0.2 and 1.0 mg/kg), and the recoveries ranged between 79.7 and 83.9% with relative standard deviation values < 6%. The method was successfully applied for the establishment of the pre-harvest residue limits (PHRL). The rate of disappearance of imidacloprid and pyrimethanil on shallot was described with first-order kinetics (imidacloprid, y(2)  = 0.9670; pyrimethanil, y(2)  = 0.9841), with half-lives of 2.87 and 2.08 days, respectively. Based on the dissipation patterns of the pesticide residues, the PHRL was recommended at 7.86 mg/kg for 14 days (PHRL14 ) and 1.98 mg/kg for 7 days (PHRL7 ) before harvest for imidacloprid, and 21.64 mg/kg for 7 days (PHRL7 ) and 9.28 mg/kg for 4 days (PHRL4 ) before harvest for pyrimethanil in shallot.
authors.affiliation: Natural Products Chemistry Laboratory, Biotechnology Research Institute, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwangju, Republic of Korea.
authors.forename: Jong-Hyouk
authors.initials: JH
authors.lastname: Park
authors.forename: Joon-Seong
authors.initials: JS
authors.lastname: Park
authors.forename: A M
authors.initials: AM
authors.lastname: Abd El-Aty
authors.forename: Md Musfiqur
authors.initials: MM
authors.lastname: Rahman
authors.forename: Tae-Woong
authors.initials: TW
authors.lastname: Na
authors.forename: Jae-Han
authors.initials: JH
authors.lastname: Shim
mesh_terms: D002853:Chromatography, Liquid / Q000191:economics / Q000379:methods; D007093:Imidazoles / Q000032:analysis*; D057230:Limit of Detection; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000032:analysis*; D010573:Pesticide Residues / Q000032:analysis; D010575:Pesticides / Q000032:analysis*; D011743:Pyrimidines / Q000032:analysis*; D027781:Shallots / Q000737:chemistry*; D052616:Solid Phase Extraction / Q000191:economics / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000191:economics / Q000379:methods*; D013997:Time Factors
chemical_list: D007093:Imidazoles; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010573:Pesticide Residues; D010575:Pesticides; D011743:Pyrimidines; C082359:imidacloprid; C108337:pyrimethanil