Simultaneous Determination of Spirotetramate and its Main Metabolite in Pistachio Using an Optimized QuEChERS Method and High Performance Liquid Chromatography

Iran is the in the first rank for pistachio production in the world. Considering the strategic importance and facilitating the export of this product, evaluation and determination of pesticide residues to ensure the safety of the product, based on the optimized and validated methods is very important. Spirotetramate is one of the newest and widely used pesticides in most of the pistachio gardens to control Agonoscena pistaciae. In order to extract this insecticide from the pistachio matrix, the optimized QuEChERS method was used. In order to save costs, all the stages of optimization of the method were performed using high performance liquid chromatography with UV detector (HPLC-UV). The optimization resulted in removal of expensive compounds like C18 and GCB, which in turn resulted in a reduction of at least 60% of the cost of extraction. All validation steps were carried out using blank pistachio samples. The samples were artificially contaminated in the laboratory with different concentrations of the insecticide. In order to confirm the final optimized method to use this method for real samples, HPLC with mass detector (LC- MS / MS) was used. At optimized conditions calibration curve of matrix effect for spirotetramate shows a good linearity in the range of 0.04- 0.10 mg/Kg (r2 of 0.995) and RSD less than 7% with the extraction recovery ranged from 85 to 100.3%. In addition, the matrix matched calibration curve for spirotetramate-enol in the above concentration range was found to have a correlation coefficient of 0.9936. The limit of quantification of the analytes was calculated to be 0.04 mg/Kg according to the SANCO guidelines, which is within the acceptable range with respect to the MRL of pistachio which is 0.05 mg/Kg.