Factors governing the removal of mancozeb residues from lettuces with washing solutions

Mancozeb was spiked in smooth and curly lettuces at two different concentrations (low and high), and lettuces were subjected to different washing treatments (with tap water, Amukine, hydrogen peroxide, acetic acid, and ammonium hydroxide) at varying time and temperature. The determination of residual levels was then carried out by using acetonitrile extraction and high performance liquid chromatography with diode array detection (HPLC-DAD). The study of analysis of variance among these experiments allowed identifying the main factors governing the removal of mancozeb residues from lettuces. In general, the oxidant character of the washing agent is the most important condition that affects removal of mancozeb from lettuces, being hydrogen peroxide more efficient than sodium hypochlorite. Moreover, other factors controlling mancozeb removal from lettuces are surface wax, concentration gradient, and also washing pH. The washing processing factor resulted to be a rest of 4% under the optima conditions (either Amukine solution for 10 min at 25 °C, or hydrogen peroxide solution for 5 min at water temperature of 15 °C).