Microwave assisted process for methidathion in water samples for physicochemical studies
A novel technique for the determination of methidathion in aqueous samples, derived from physicochemical studies of pesticides in soil, has been developed. Experimental designs have been the tool used for the optimisation of the microwave process. Recoveries of 95 ± 2.1% were obtained when 1 ml spiked water sample with methidathion at 5 mg l−1 was microwave extracted with 2 ml hexane–toluene (1 + 1) for 100 s at 50% power. The simultaneous analysis of 24 samples allowed a quantitative extraction of the pesticide. The method, compared with classical procedures, like liquid–liquid microextraction or vortex mixture, provided higher recoveries for the three organophosphorus pesticides, methidathion, malathion and azinphos-methyl, being for the latter three times higher than the classical procedures. Detection limits for the chromatographic determinations were of 1.1 mg l−1 for malathion, 0.65 mg l−1 for methidathion and 1.86 mg l−1 for azinphos-methyl.