title: [Determination of eight pesticide residues in tea by liquid chromatography-tandem mass spectrometry and its uncertainty evaluation].
abstract: A method was developed for the determination of eight pesticide residues (fipronil, imidacloprid, acetamiprid, buprofezin, triadimefon, triadimenol, profenofos, pyridaben) in tea by liquid chromatography-tandem mass spectrometry. The sample was extracted by accelerated solvent extraction with acetone-dichloromethane (1:1, v/v) as solvent, and the extract was then cleaned-up with a Carb/NH2 solid phase extraction (SPE) column. The separation was performed on a Hypersil Gold C, column (150 mm x 2. 1 mm, 5 microm) and with the gradient elution of acetonitrile and 0. 1% formic acid. The eight pesticides were determined in the modes of electrospray ionization (ESI) and multiple reaction monitoring (MRM). The analytes were quantified by matrix-matched internal standard method for imidacloprid and acetamiprid, by matrix-matched external standard method for the other pesticides. The calibration curves showed good linearity in 1 - 100 microg/L for fipronil, and in 5 -200 microg/L for the other pesticides. The limits of quantification (LOQs, S/N> 10) were 2 p.g/kg for fipronil and 10 microg/kg for the other pesticides. The average recoveries ranged from 75. 5% to 115.0% with the relative standard deviations of 2.7% - 7.7% at the spiked levels of 2, 5, 50 microg/kg for fipronil and 10, 50, 100 microg/kg for the other pesticides. The uncertainty evaluation for the results was carried out according to JJF 1059-1999 "Evaluation and Expression of Uncertainty in Measurement". Items constituting measurement uncertainty involved standard solution, weighing of sample, sample pre-treatment, and the measurement repeatability of the equipment were evaluated. The results showed that the measurement uncertainty is mainly due to sample pre-treatment, standard curves and measurement repeatability of the equipment. The method developed is suitable for the conformation and quantification of the pesticides in tea.
authors.affiliation: Shaoxing Entry-Exit Inspection and Quarantine Bureau, Shaoxing 312000, China. huebizhen_002@yahoo.com.cn
authors.forename: Beizhen
authors.initials: B
authors.lastname: Hu
authors.forename: Haijiang
authors.initials: H
authors.lastname: Cai
authors.forename: Weihua
authors.initials: W
authors.lastname: Song
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D005506:Food Contamination / Q000032:analysis*; D007093:Imidazoles / Q000032:analysis; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000032:analysis; D010573:Pesticide Residues / Q000032:analysis*; D011720:Pyrazoles / Q000032:analysis; D011725:Pyridines / Q000032:analysis; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013662:Tea / Q000737:chemistry*; D035501:Uncertainty
chemical_list: D007093:Imidazoles; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010573:Pesticide Residues; D011720:Pyrazoles; D011725:Pyridines; D013662:Tea; C082359:imidacloprid; C464485:acetamiprid; C082360:fipronil