Fresh tomatoes were cleaned, cut into small pieces and
homogenized in a stainless steel blender. A 2.0 g aliquot of homogenized sample was accurately
weighed, placed in a 15 mL plastic centrifuge tube with conical bottom, and then centrifuged at
4000 rpm for 2 min. The resulting supernatant was collected and diluted to the volume of 10 mL
with ultrapure water. Finally, the pH of the sample solution was adjusted to 6.0 with 1 mol L - 1
hydrochloric acid and 1 mol L - 1 sodium hydroxide solution.
For the spiked samples, the above procedure was carried out and then followed by adding specific
volumes of standard solu- tions of carbamate pesticides. The mixture was shaked for 10 min and
equilibrated at room temperature for about 3 h before the
analysis.