Analysis of residues of imidacloprid in tobacco by high‐performance liquid chromatography with liquid–liquid partition cleanup

Abstract

A practical method for analysis of residues of imidacloprid in baked tobacco leaves has been developed using HPLC with liquid–liquid partition clean‐up. Imidacloprid was extracted with ethyl acetate under ultrasound, and cleaned up by liquid–liquid partition with 50 g litre⁻¹ aqueous sodium chloride followed by dichloromethane. The water‐soluble and fat‐soluble components in tobacco, which interfere with imidacloprid in HPLC, were removed. The separation was performed on a Supelco LC‐18 column (250 mm × 4.6 mm ID) with a mobile phase of acetonitrile + 5 mM ammonium acetate (20 + 80 by volume) at a flow‐rate of 1 ml min⁻¹. The baseline separation between imidacloprid and the tobacco blank was achieved within 10 min. With a detection wavelength at 270 nm, the limit of quantitation was 0.04 mg kg⁻¹. The recovery ranged from 89.8 to 95.4% and the RSDs were less than 2.3%. The proposed method was successfully employed for the determination of imidacloprid residues in 300 samples of flue‐cured tobacco leaves. Copyright © 2004 Society of Chemical Industry