title: Residual dynamics of thiacloprid in medical herbs marjoram, thyme, and camomile in soil.
abstract: Thiacloprid is a new insecticide of the chloronicotinyl family. To assess its risk after application, residual characteristics of thiacloprid in marjoram, thyme, and camomile and in soil were studied under field conditions. The active ingredient was extracted from the plant material using a mixture of acetone-water. After filtration, the extract was concentrated to the aqueous phase, diluted with water, and portioned against ethyl acetate on a matrix solid phase dispersion column. Thiacloprid was extracted from soil using a mixture of methanol-water, filtered, and reextracted (clean up) with dichloromethane. The residues were quantified using HPLC-MS-MS. The methods were validated by recovery experiments. Thiacloprid residues in marjoram, thyme, and camomile and in soil persisted beyond 10, 14, 14, and 21 d but no residues were detected after 14, 21, 21, and 28 d, respectively. The data obtained in this study indicated that the biexponential model is more suitable than the first-order function to describe the decline of thiacloprid in fresh marjoram, fresh thyme, and dried camomile flowers with half-life (t1/2) of 1.1, 0.7, and 1.2 d, respectively. However, both the first-order function and biexponential model were found to be applicable for dissipation of thiacloprid in soil with almost the same t1/2 values of 3.5 and 3.6 d. The results indicated that thiacloprid dissipates rapidly and does not accumulate in the tested herbs and in soil.
authors.affiliation: Department of Plant Protection, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310029, China. ylyu@zju.edu.cn
authors.forename: Yun-long
authors.initials: YL
authors.lastname: Yu
authors.forename: Jia-lun
authors.initials: JL
authors.lastname: Wu
authors.forename: Matthias
authors.initials: M
authors.lastname: Stahler
authors.forename: Wilfried
authors.initials: W
authors.lastname: Pestemer
mesh_terms: D020843:Chamomile / Q000378:metabolism*; D004784:Environmental Monitoring; D035264:Flowers / Q000378:metabolism; D007306:Insecticides / Q000032:analysis / Q000378:metabolism*; D000073943:Neonicotinoids; D031341:Origanum / Q000378:metabolism*; D010573:Pesticide Residues / Q000032:analysis / Q000378:metabolism; D010946:Plants, Medicinal / Q000378:metabolism; D011725:Pyridines / Q000032:analysis / Q000378:metabolism*; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism*; D013843:Thiazines / Q000032:analysis / Q000378:metabolism*; D046930:Thymus Plant / Q000378:metabolism*
chemical_list: D007306:Insecticides; D000073943:Neonicotinoids; D010573:Pesticide Residues; D011725:Pyridines; D012989:Soil Pollutants; D013843:Thiazines; C417209:thiacloprid