Abstract: An online column enrichment-ultra high performance liquid chromatography (UHPLC) method was developed to determine trace carbaryl and carbofuran in water. The sample was injected into a UHPLC system directly after filtration with 0.22 μm membrane, and then enriched by online solid phase extraction (SPE) column. The analyte was back-flushed into the analytical column Acclaim RSLC C18 (100 mm×2.1 mm, 2.2 μm) by valve switching method. The mobile phases were 10 mmol/L ammonium acetate buffer (pH 5.0, adjusted by acetic acid) and acetonitrile in a gradient elution mode with a flow rate of 0.8 mL/min, and detected by a diode array detector with the detection wavelength of 280 nm. The good linear ranges of carbaryl and carbofuran were 1.0~100 μg/L with the correlation coefficients (r2) larger than 0.9999, and the limits of detection (S/N=3) were 0.5 μg/L and 0.25 μg/L, respectively. The average spiked recoveries were in the range of 76.0%~120.0%. The method has been applied to determine trace carbaryl and carbofuran in water samples with satisfactory results.

Key words: carbaryl, carbofuran, online column enrichment, ultra high performance liquid chromatography (UHPLC), dual gradient