Determination of Degradation Rate of Acaricide Fenpyroximate in Apple, Citrus, and Grape by HPLC-DAD

Fenpyroximate, a widely used acaricide around the world, was recently registered for control of mites in Egypt. Hence, only limited data are available on the dissipation rate of fenpyroximate under field conditions. In this study the dissipation rate of fenpyroximate after one application on apple, citrus and grape was estimated. Samples were prepared by an optimized quick, easy, cheap, effective, rugged, and safe (QuEChERS) analytical method before quantification by high performance liquid chromatography with diode array detector (HPLC-DAD). The initial deposit of fenpyroximate residue of 1.63, 0.33, 0.49 and 1.75 mg kg(-1) on apple, citrus, grape fruits and grape leaves, respectively after 7 days of application degraded to 0.14 mg/kg (91.41%), 0.09 mg kg(-1) (72.7%), 0.08 mg kg(-1) (83.6%) and 0.07 mg kg(-1) (96.0%), respectively. Preharvest interval (PHI) and maximum residue limit (MRL) were: 7 days and 0.3 mg kg(-1) for apple, 3 days and 0.2 mg kg(-1) for citrus, 3 days and 0.2 mg kg(-1) for grape fruits, and 14 days and 0.2 mg kg(-1) for grape leaves. Dissipation rate for all fruits followed first order kinetics with half-lives (t(1/2)) of 2.03, 2.42, 1.56 and 2.75 days for apple, citrus, grape fruits and grape leaves, respectively. We suggested that a waiting period of at least 3 days before harvesting the citrus and grape fruits and 7 days for apple and 17 days for grape leaves after fenpyroximate application at recommended dose that may be considered quite safe from point of health hazards due to the toxic effect of residues.