Determination of Imidacloprid residues by SPE - HPLC - MS/MS in bovine tissues. Tune-up and validation of the analytical technique

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

Santa Fe

Congreso; 2nd Latin American Pesticide Residue Workshop; 2009

Imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine] is a member of the chloronicotinyl neonicotinoid compounds. It was introduced into commercial use in 1990. It is the most important systemic insecticide and has a wide diversity of uses in agriculture and veterinary medicine. Several methods have been reported for the analysis of Imidacloprid that employ gas chromatography and high-performance liquid chromatography (HPLC).The objective of this work is to develop a new extraction scheme (SPE) coupled to a HPLC-MS/MS methodology in order to detect and quantify Imidacloprid residues in bovine tissues with fully valid procedures.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 bovine 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 column used was a Hypersil Gold (Thermo), 100x2.1 mm, 3 um. For cleanup, an online SPE column was used, Oasis HLB (Waters), 2.1x20 mm, 25 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 bovine tissue) were between 62 and 102% with a relative standard deviation between 3 and 12%. Calibration curves were linear from 150 to 2800 ug/kg. The detector linearity (r2> 0.995) and the repeatability (4 - 10%) of the method proved to be very precise. The limits of quantification were variable between different matrices ranged from 38 and 107 ug/kg.Samples of different bovine (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.