Abstract: A new resonance light scattering (RLS) method for the rapid determination of residual chlorpyrifos in vegetables such as Chinese leek, amaranth, sweet potato, and black cabbage was developed based on the reaction of chlorpyrifos with crystal violet-potassium iodide in Britton-Robinson butter at pH 11.00 to generate an ion association complex. Chlorpyrifos had maximum resonance light scattering peak at 650 nm. A good liner relationship (r = 0.9981) was observed between chlorpyrifos concentration over the range of 0.016–0.877 μg/mL and relative scattered light intensity. The detection limit of chlorpyrifos was 0.016 μg/mL and the relative standard deviations (RSDs) of precision for 5 replicate determinations were less than 2.5%. The average recovery rates of chlorpyrifos in four vegetables were 91.4%–100.3% (n = 5). This method was simple, rapid and sensitive and satisfying results were obtained in its practical applications.

Key words: resonance light scattering, chlorpyrifos, crystal violet-potassium iodide, vegetables