Capillary liquid chromatography as an effective method for the determination of seven neonicotinoid residues in honey samples

A new analytical method based on capillary liquid chromatography with diode array detection has been developed for the simultaneous quantification of seven neonicotinoid insecticides commercially available (imidacloprid, thiacloprid, clothianidin, thiamethoxam, acetamiprid, nitenpyram, and dinotefuran) in honey samples. The separation was achieved in a Zorbax XDB-C18 column (150 x 0.5 mm id, 5 mu m), with a mobile phase consisting of ultrapure water (solvent A) and acetonitrile (solvent B) at a flow rate of 10 mu L/min. Capillary column was thermostated at 25 degrees C during the analysis and 254 or 270 nm was established as detection wavelength, depending on the analyte. Furthermore, full loop injection mode (8 mu L) was selected, using water as injection solvent. Finally, the optimized method was applied to the analysis of neonicotinoid residues in honey of different floral origins using dispersive liquid-liquid microextraction as sample treatment. Variables affecting the extraction efficiency were optimized, choosing methanol and dichloromethane as dispersive and extraction solvents, respectively. The method was characterized in terms of linearity (R2 >= 0.9948), repeatability, reproducibility (relative standard deviation below 4.5 and 6.3% respectively), and recoveries (>= 80.5%). Detection and quantification limits were lower than 6.6 and 22.0 mu g/kg for the studied analytes, respectively.