Schiff base networks (SNWs) were introduced as a new stir bar coating, and a method of SNWs- coated stir bar sorptive extraction (SBSE) coupled to high performance liquid chromatography-ultraviolet detector (HPLC-UV) was developed for determination of pyrethroid pesticide residues in tobacco. The prepared amorphous SNWs polymer from melamine and 3,5-dihydroxybenzaldehyde riches in triazine rings, hydroxyl groups and amino groups, and the SNWs/polydimethylsiloxane (PDMS) stir bar prepared by sol-gel method can extract weakly polar pyrethroid pesticides through hydrophobic, π-π and hydrogen bonding. The SNWs/PDMS stir bar exhibited high extraction efficiency toward pyrethroid pesticides (70-76%) and good mechanical stability with reused time more than 50 times. Under the optimal experimental conditions, the limits of detection were 0.20 - 0.66 µg/L with relative standard deviation varying in the range of 2.3-8.2%, which meets the requirements of trace analysis of pesticide residues in the tobacco industry. The method was applied to the determination of six pyrethroid pesticides in cigarette samples, and the recovery for the spiked samples ranged from 82 to 117%, showing a great applicability for the analysis of pesticide residues in real samples with a complex sample matrix.
Keywords: HPLC-UV; Pyrethroids; Schiff base networks; Stir bar sorptive extraction; Tobacco.
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