Multi-residue method for determination of seven neonicotinoid insecticides in grains using dispersive solid-phase extraction and dispersive liquid-liquid micro-extraction by high performance liquid chromatography

A method using dispersive solid-phase extraction and dispersive liquid-liquid micro-extraction cleanup followed by high performance liquid chromatography (HPLC) has been established for determination of seven neonicotinoid insecticides residues in grains including brown rice, maize, millet and oat. Based on an appraisal of the characteristics of HPLC, validation experiments were conducted for seven neonicotinoid insecticides. In the method, dispersive solid-phase extraction was carried out using PSA and bonded C ₁₈ coupled with graphitised carbon black with acetonitrile as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R ² ≥ 0.99. At the low, medium and high three fortification levels of 0.05-0.8 mg kg ^-1, recoveries fell within 76-123%. The relative standard deviation was between 0.9% and 12.6% for seven neonicotinoid pesticides. Low limits of detection (0.002-0.005 mg kg ^-1) and quantification (0.007-0.018 mg kg ^-1) were readily achieved with this method for all tested pesticides.