Parathion and EPN residue studies on Concord grapes.

Loss of parathion and EPN deposits from the fruit of the Concord grape was determined over a period of 3 weeks following the final application of three-spray programs. Deposits of EPN persisted somewhat longer than those of parathion. The presence of hydrated lime in the spray mixture caused no appreciable increase in rate of loss. A complication was encountered in making determinations on maturing Concord grapes by the Averell & Norris (1948, Analyt. Chem., vol. 20, p. 753) method. This evidence suggests that a color interference in the Fruit s caused by the removal of the methyl anthranilate by the benzene used as a solvent to remove the insecticide deposit. This compound, to a large extent, can be removed by washing the benzene strip several times with 10% hydrochloric acid.