Degradation behaviour of methamidophos and chlorpyrifos in apple juice treated with pulsed electric fields

Apple juice (13 degrees Brix) spiked with methamidophos and chlorpyrifos (2-3 mg/l of each compound) was treated by pulsed electric fields (PEF), and pesticide residues were quantified by gas chromatography with flame photometric detection (GC-FPD). Results showed that electric field strength (8-20 kV/cm) and pulse number (6-26 pulses) have significant effects on the degradation of methamidophos and chlorpyrifos. PEF treatment is effective for the degradation of methamidophos and chlorpyrifos residues in apple juice, and chlorpyrifos is much more labile to PEF than methamidophos. An increase in either pulse number or electric field strength could speed the degradation of methamidophos and chlorpyrifos, and the kinetics equations and related parameters quantitatively characterized the degradation behavior of the pesticides. The exponential model better fits the experimental data for all treatments than the linear model. (C) 2008 Elsevier Ltd. All rights reserved.