title: Evaluation of direct analysis in real time for the determination of highly polar pesticides in lettuce and celery using modified Quick Polar Pesticides Extraction method.
abstract: Direct analysis in real time (DART) was evaluated for the determination of a number of highly polar pesticides using the Quick Polar Pesticides Extraction (QuPPe) method. DART was hyphenated to high resolution mass spectrometry (HRMS) in order to get the required selectivity that allows the determination of these compounds in complex samples such as lettuce and celery. Experimental parameters such as desorption temperature, scanning speed, and distances between the DART ion source and MS inlet were optimized. Two different mass analyzers (Orbitrap and QTOF) and two accessories for sample introduction (Dip-it®tips and QuickStrip™ sample cards) were evaluated. An extra clean-up step using primary-secondary amine (PSA) was included in the QuPPe method to improve sensitivity. The main limitation found was in-source fragmentation, nevertheless QuPPe-DART-HRMS proved to be a fast and reliable tool with quantitative capabilities for at least seven compounds: amitrole, cyromazine, propamocarb, melamine, diethanolamine, triethanolamine and 1,2,4-triazole. The limits of detection ranged from 20 to 60μg/kg. Recoveries for fortified samples ranged from 71 to 115%, with relative standard deviations <18%.
authors.affiliation: Department of Analytical Chemistry, Faculty of Sciences, University of Granada, Campus Fuentenueva s/n, 18071 Granada, Spain. Electronic address: frjlara@ugr.es.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Lara
authors.affiliation: Fera Science Ltd, Sand Hutton, York, YO41 1LZ, United Kingdom.
authors.forename: Danny
authors.initials: D
authors.lastname: Chan
authors.affiliation: Fera Science Ltd, Sand Hutton, York, YO41 1LZ, United Kingdom.
authors.forename: Michael
authors.initials: M
authors.lastname: Dickinson
authors.affiliation: Fera Science Ltd, Sand Hutton, York, YO41 1LZ, United Kingdom.
authors.forename: Antony S
authors.initials: AS
authors.lastname: Lloyd
authors.affiliation: Fera Science Ltd, Sand Hutton, York, YO41 1LZ, United Kingdom.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Adams
mesh_terms: D000077102:Apium / Q000737:chemistry*; D002138:Calibration; D018545:Lactuca / Q000737:chemistry*; D010573:Pesticide Residues / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification; D010575:Pesticides / Q000032:analysis* / Q000737:chemistry* / Q000302:isolation & purification; D013696:Temperature; D013997:Time Factors
chemical_list: D010573:Pesticide Residues; D010575:Pesticides
keywords: Direct analysis in real time; High resolution mass spectrometry; Polar pesticides; Quick Polar Pesticides Extraction; Vegetable samples