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Silica nanoparticles (SiNPs) have been used as concentrating probes to extract paraquat and diquat from aqueous solution before capillary electrophoretic analysis.Adsorption of paraquat and diquat onto SiNPs is mainly through electrostatic interaction.After extraction and centrifugation, the analytes were eluted from the surface of SINPs by rinsing with acetic acid solution.The extract was directly analyzed by capillary electrophoresis with UV absorption detection.Using SiNPs to concentrate the analytes from 10 mL of aqueous solution, the enrichment factors for paraquat and diquat were 75 and 192, respectively.The limits of detection (LODs) at signal-to-noise ratio of 3 were 0.03 and 0.05 μM for paraquat and diquat, respectively.This developed method was applied to the determination of paraquat in mung bean.The LOD of paraquat in mung bean was 0.1 μg/g.