Simultaneous determination of imidacloprid and carbendazim in water samples by ion chromatography with fluorescence detector and post-column photochemical reactor

A new analytical method has been developed and validated for the simultaneous determination of pesticides from different classes using ion chromatography-online photochemical derivatisation-fluorescence detector (IC-hv-FD). Fluorimetric detection was performed at λex/λem=332 nm/367 nm for imidacloprid and then detector was set at λex/λem=247 nm/470 nm for carbendazim. The two pesticides imidacloprid and carbendazim were successfully separated isocratically on an IonPac® AS11 (250 mm×4 mm i.d; 13 µm particle size, Dionex) anion-exchange column using 40 mM KOH with 10% (v/v) acetonitrile and pumped at a flow rate of 1.0 mL min−1. Under the optimized conditions, the limit of detection (LOD, S/N=3) of imidacloprid and carbendazim were 7.8 µg L−1 and 67 µg L−1, respectively. The experimental results showed that there was good linearity with a correlation coefficient (r)≥0.9966 over the range of 0.05-10 mg L−1 for imidacloprid and 0.2-15 mg L−1 for carbendazim. Good reproducibility with a relative standard deviation (RSD, n=7) less than 4.5%. Finally, the proposed method was applied with satisfactory results to the analysis of these pesticides in ground water, lake water and river water without any pre-treatment of samples. The average spiked recoveries were in the range of 90-104%.