A novel inhibitory kinetic fluorimetric method for the determination of trace methomyl in environmental samples

A novel inhibitory kinetic fluorimetric method for the determination of trace methomyl was proposed. It was shown that the Fenton reagent oxidized rhodamine B in acid medium which enabled the fluorescence quenching of the latter. The presence of trace methomyl clearly inhibited the reaction. Upon addition of EDTA, a good linear relationship between the inhibitory effect and the concentration of methomyl was observed, together with improved stabilization and sensitivity. Factors affecting the determination of trace methomyl were investigated systematically. Under the optimum conditions, the linear range for the determination of methomyl was 0.04-2.2 microg/mL; the detection limit and the quantification limit for methomyl were 0.011 and 0.037 microg/mL, respectively. The proposed method was applied to the determination of methomyl in four environmental soil samples, six environmental water samples and one synthetic sample; the results were compared with those determined by the HPLC method. The recoveries and the relative errors were 83.5-101.2 and 0.47-2.02%, respectively. The possible reaction mechanism has also been discussed.