Multiresidue determination in soil of pesticides used in tomato crops by sonication-assisted extraction in small columns and gas chromatography

Various herbicides and insecticides belonging to different chemical groups and used in tomato crops were determined in soil. The proposed analytical method was based on the sonication-assisted extraction in small columns (SAESC) of pesticides using ethyl acetate. All pesticides were determined by capillary gas chromatography with electron-capture detection (GC-ECD) and their identity was confirmed by gas chromatography coupled with mass spectrometry (GC-MS). Recoveries obtained for all compounds in the two soils studied varied from 81 to 106% with a relative standard deviation between 2 and 9%. The limit of detection in the conditions assayed was at least 0.01 mug/g for all compounds. The developed procedure was applied to the analysis of real samples, obtained after tomato harvest, from 18 commercial fields in Spain, and residue levels of pendimethalin (0.018-0.650 mug/g) endosulfan-I (0.011-0.032 mug/g), endosulfan-II (0.014-0.178 mug/g) and endosulfan-sulfate (0.010-0.135 mug/g) were found.