title: Analysis of pesticide residues in lettuce by large volume-difficult matrix introduction-gas chromatography-time of flight-mass spectrometry (LV-DMI-GC-TOF-MS).
abstract: A multi-residue method is described that eliminates the need for a clean-up step and thus allows the rapid determination of pesticides in crude extracts of lettuce. Samples were extracted with a mixture of ethyl acetate, Na2SO4 and NaHCO3 and the crude extracts analysed directly using large volume-difficult matrix introduction (LV-DMI) in combination with gas chromatography-time of flight-mass spectrometry (GC-TOF-MS). The LV-DMI procedure described was evaluated for the analysis of dimethoate, pyrimethanil, chlorothalonil, vinclozolin, furalaxyl and oxadixyl. Satisfactory response was obtained at the lowest calibrated level (LCL) of 0.0025 microg ml(-1), with good linearity over the range 0.0025-0.5 microg ml(-1) (0.005-1.0 mg kg(-1) equivalent). Average recoveries between 73 and 118% were obtained at the 0.01-0.5 mg kg(-1) levels with RSD values < or = 13%.
authors.affiliation: Central Science Laboratory, Sand Hutton, York, UK YO41 1LZ.
authors.forename: Katan
authors.initials: K
authors.lastname: Patel
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Fussell
authors.forename: David M
authors.initials: DM
authors.lastname: Goodall
authors.forename: Brendan J
authors.initials: BJ
authors.lastname: Keely
mesh_terms: D002849:Chromatography, Gas / Q000379:methods; D001330:Electronic Data Processing / Q000379:methods; D018545:Lactuca / Q000737:chemistry*; D010080:Oxazoles / Q000032:analysis; D010573:Pesticide Residues / Q000032:analysis*; D011743:Pyrimidines / Q000032:analysis; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D010080:Oxazoles; D010573:Pesticide Residues; D011743:Pyrimidines; C108337:pyrimethanil; C025643:vinclozolin