Degradation of azoxystrobin, boscalid, and chlorpyrifos residues on strawberries using vapor-phase chlorine radical advanced oxidation process.

Various advanced oxidative processes (AOPs) have been developed to remove disease-causing pathogens from the surface of fruits and vegetables. Few studies have investigated the effect of these AOPs on pesticide residues that may also be present on fruits and vegetables. This study validated methods using gas and liquid chromatography and mass spectrometry to measure two fungicides (azoxystrobin and boscalid) and one insecticide (chlorpyrifos) in strawberries that have been treated using a vapor-phase chlorine radical advanced oxidation process (AOP). These three pesticides were chosen as their residues have been detected in strawberries grown in North America. The validated limits of detection for the three pesticides were ≤ 0.3 µg/g of strawberry tissue. The AOP used in this study had been previously optimized for the elimination for the disease-causing pathogens (e.g., Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella) on fruits and vegetables. To examine the effect of this AOP on pesticide residues, strawberries were spiked with a known amount of each pesticide and exposed to vapor phase chlorine-radical AOP consisting of UV-C, ozone, and electrolyzed water containing free chlorine from 30 s to 30 min. The vapor-phase chlorine radical AOP was able to degrade the pesticides on the surface of strawberries, but the amount of degradation varied among the pesticides. Azoxystrobin and chlorpyrifos were degraded up to an average of 35 and 48%, respectively, while boscalid was degraded on average by 13%. The absorbance of pesticides into the strawberry could have limited the degradation by the vapor-phase chlorine radical AOP, which mainly acts at the surface of the fruit.