Pesticide determination in tomatoes by solid–liquid extraction with purification at low temperature and gas chromatography

In this work, a simple and low cost method, based on solid–liquid extraction with low temperature purification (SLE–LTP), was optimized and validated for the determination of chlorpyrifos, λ-cyhalothrin, cypermethrin and deltamethrin in tomato samples. The analyses were performed by the GC–ECD and confirmed by the GC–MS. The method requires 4 g of tomato and an extraction mixture (8.0 mL acetonitrile, 0.5 mL water and 1.5 mL ethyl acetate), which was established by mixture experimental design. After optimization, pesticide recovery rates ranged from 79% to 97%, with a standard deviation of less than 5%. The SLE–LTP analytical characteristics were compared very favorably to the matrix solid phase dispersion technique, which used ethyl acetate and Florisil for extraction.