Pesticide determination by stopped-flow fluoroimmunoassay using Cresyl Violet as label Original Research Article

A homogeneous stopped-flow fluoroimmunoassay method based on the use of Cresyl Violet as label is described for the first time and applied to the determination of the pesticide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). The tracer showed an increase in its fluorescence intensity when reacted with the antibody, so that the initial rate of this reaction and the equilibrium signal were used as the analytical parameters, which were measured in 2 and 50 s, respectively. The dynamic range of the calibration graph obtained for the proposed kinetic and equilibrium methods were 0.02–10 ng ml−1 and 0.1–100 ng ml−1, respectively, and the detection limits achieved were 6 and 30 pg ml−1, respectively. The relative standard deviation was close to 3%. The recoveries obtained by applying the method to several spiked liquid food samples (spring water, white wine and grape juice) ranged from 94.4% to 105.6%.