Determination of residual Imidacloprid in ovine tissues using solid phase extraction - liquid chromatography coupled with electrospray ionization tandem mass spectrometry

M. M. YOSSEN, G. A. HUNZICKER, J. BARRANDEGUY, D. F. LENCINA, M. C. DOMÍNGUEZ

Santa Fe

Congreso; 2nd Latin American Pesticide Residue Workshop; 2009

Imidacloprid [1-(6chloronicotinyl)-2-(nitroimino)imidazolidine] is a member of the chloronicotinyl neonicotinoid compounds that acts on the central nervous system of the insects. It was introduced into commercial use in 1990, and has a wide diversity of uses in agriculture and veterinary medicine. Several methods have been reported for the analysis of Imidacloprid residues, by derivatization and gas chromatography, or high-performance liquid chromatography (HPLC).The objective of this work is to validate the analytical tecnique SPE-HPLC-MS/MS in order to detect and quantify Imidacloprid residues in different ovine (adipose, hepatic, muscular and renal) tissues at the maximum residue limits (MRL).Chemicals, Reagents and Extraction Method. HPLC grade solvents were used. Imidacloprid standard (purity 95.3%; Romikin). Stock standard solution for Imidacloprid was prepared in acetonitrile (ACN) and stored at 4 °C in the dark, where it is stable for several weeks. Calibration solution was prepared from dilution of the standard solution in ACN. Working standard solutions in matrix were prepared by spiking an adequate amount of blank ovine tissue with different aliquots of the calibration solution. Then, after homogenization, extraction with ACN, and centrifugation, different Imidacloprid concentration matrix extracts were obtained.The HPLC - MS/MS system consisted of a ProStar 210 (Varian Inc.) HPLC chromatograph equipped with an in-line degasser (Degassit Metachem Inc.) and an autosampler ProStar 410 (Varian Inc.) connected to a Varian 1200L tandem quadrupole mass spectrometer equipped with an electrospray ionization (ESI) interface (Varian Inc.). The columns used were: i) for cleanup, online SPE column Oasis HLB (Waters), 2.1 x 20 mm, 25 um; ii) analytical: Hypersil Gold (Thermo), 100 x 2.1 mm, 3 um. Further, a homogenizer (Pro 200), a vortex (Boeco) and a refrigerated centrifuge (Eppendorf 5702R) were used.The overall recoveries for Imidacloprid, from different matrices (adipose, hepatic, muscular and renal ovine tissue) were between 79 and 114 % with a relative standard deviation between 5 and 11 %. Calibration curves were linear from 150 to 2800 ug/kg. The detector linearity (r2> 0.995) and the repeatability (4 - 6 %) of the method proved to be very precise. The limits of quantification were variable between different matrices ranged from 37 and 146 ug/kg.Samples of different ovine (adipose, hepatic, muscular and renal) tissues were analyzed by the proposed SPE-HPLC-MS/MS method. The analytical results showed no quantifiable residues in any sample material.