RESUMEN
A sensitive high performance liquid chromatographic method using ultraviolet detector has been developed for the determination of methomyl insecticide residues on tomato and cucumber fruits. The developed method consisted of extraction with ethyl acetate, adsorption clean up [by adsorbing mixture consisting of charcoal/celite in ratio 2: 1], followed by high performance liquid chromatographic determination using methanol: water [1: 1] as a mobile phase and UV detection at 233 nm. The range of percentage recovery was between 88.2% and 90.4% for both plant samples. [These recoveries are good for those types of extraction of pesticides traces from plant materials, refer to [1] to compare recoveries]. The method was applied to determine residues and rate of decline of methomyl from fruits of tomatoes and cucumber [open field and greenhouse treatment, with methomyl formulation [Lannate 90% SP] for 100 liter water]. The insecticide incorporated into the plants decreased rapidly with a half-life around 1 day in winter and 0.5 day in summer