Optimization of superheated water extraction of some pesticides from sand soil sample (in Thai)

In this study the extraction of pesticides, namely butachlor, malathion, metalaxyl, propiconazole and thiobencarb, from sand samples was performed by using subcritical water extraction. The condition such as extraction temperature, extraction time and trapping organic solvent were optimized and the extractant was further analysed by a gas chromatograph equipped with flame ionization detector (GC-FID). The optimum temperature for extracting butachlor, malathion, metalaxyl and propiconazole was 160degreesC, but that for thiobencarb was 180degreesC. The optimum static and dynamic times of butachlor, propiconazol and thiobencarb were both 20 min, those of metalaxyl were 15 and 10 min, and those of malathion were 5 and 20 min, respectively. The suitable trapping solvent for all pesticides was dichloromethane. With the above optimum conditions for each pesticides, the overall removal of the pesticides from sand were as followed: 98.98% butachlor, 100.95% propiconazole, 103.34% thiobencarb, 97.50% malathion and. 99.11% metalaxyl.