Persistence of some Systemic and Non-systemic Pesticides in Potato after Field Application and throughout Food Processing

This research aimed to study the persistence of some systemic pesticides; dimethoate and methomyl, and non-systemic pesticides; diazinon and mancozeb in potato after field application and impact of different washing and soaking treatments and some thermal processes in removal of tested pesticides. Treated potato samples were collected at (3 hour), 1, 3, 5, 7, 14, and 21 days after pesticides treatment. Potato samples were soaked in tap water and different chemical solutions of acetic acid and NaCl, also potato slices were blanched, cooked by stewing and fried. Data indicated that the average recovery percent of dimethoate and diazinon determined by GC were 94.05 and 95.69. While, in the case of methomyl and mancozeb determined by HPLC were 85.86 and 96.01% in potato; respectively. Systemic pesticides; dimethoate and methomyl showed that high persistence rates in potato tubers after application which dissipated to (0.501 and 0.366 mg/kg) after 14 days of treatment compared with initial residues (3.682 and 3.190 mg/kg); respectively and there were still above the MRLs. Contrary, non-systemic pesticides; diazinon and mancozeb showed that high dissipation rates after application which decreased to (0.068 and 0.109 mg/kg) after 14 days of treatment compared with (4.211 and 3.820 mg/kg) at initial residues and there were below the MRLs. Also washing by soaking in 5% acetic acid solution more effective in pesticide residues removal which removed (51.75% - 61.93%) compared with other washing treatments. In addition, cooking and frying processes caused complete removing of tested systemic and non-systemic pesticide' residues from potato tubers.