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Imidacloprid Extraction from Citrus Leaves and Analysis by Liquid Chromatography–Mass Spectrometry (HPLC–MS/MS)

Leiva, Jorge A., Nkedi-Kizza, Peter, Borejsza-Wysocki, Wlodzimierz S., Bauder, Victor S., Morgan, Kelly T.
Bulletin of environmental contamination and toxicology 2016 v.96 no.5 pp. 671-677
Citrus, Diaphorina citri, control methods, detection limit, imidacloprid, leaves, liquid chromatography, mass spectrometry, methanol, mortality, soil drenching, stainless steel, trees
A procedure was developed to extract Imidacloprid (IMD) from newly-flushed and fully-expanded citrus leaves. The extraction was conducted in a bullet blender, using a small sample mass (0.5 g of fresh tissue), stainless-steel beads (24 g), and methanol as extractant (10 mL). The extracts did not require further clean-up before analysis by HPLC–MS/MS. The method was validated with control samples from IMD-untreated Hamlin orange trees. The method limit of detection and limit of quantitation were 0.04 and 0.12 μg g⁻¹, respectively. IMD recoveries from fortified leaf tissue were between 92 % and 102 %, with relative standard deviations of <8 %. The method was further evaluated by extracting leaves from Hamlin orange trees treated with IMD. The treated trees showed maximum concentrations of 10.8 and 21.8 µg g⁻¹, observed at 20 days after applying two soil-drenching rates (0.51 and 1.02 kg IMD ha⁻¹), respectively. This extraction technique will generate useful data on IMD plant uptake, foliar concentration, and correlations with Asian citrus psyllid (ACP) mortality or control. The method could be used to generate baseline data to improve IMD soil-drenching applications as the main management practice to control the ACP.