Analysis of organochlorine and organophosphate pesticide residues in cabbage

Compounds present in cabbage (Cruciferae, family, genus Brassica, genus Brassica, variety capitata) which interfere with pesticide analysis by an electron capture detector on a gas liquid chromatograph were investigated. The interfering compounds were found to be present throughout various segments of the cabbage head as well as in cabbage grown in different geographical areas under different growing condition. During storage of the cabbage up to 40 days at 2°C prior to analysis, the interfering compounds decreased in concentration. After 16 days storage, some compounds disappeared while other compounds appeared; however, some interference remained up to 40 days of storage. Various treatments which did not remove the interference included: heat, and different clean-up methods by florisil columns, and acid-celite column, and an ion-exchange column. Mass spectrometry of interference from cabbage indicated the presence of N-octadecane, the existence of long chain hydrocarbon waxes, and the existence of alkyl substituted benzene rings. Mass spectrometry showed that volatiles which are a part of cabbage flavor (sulfur containing) or various pesticides were not the interfering compounds.

Recovery studies of organochlorine and organophosphate pesticides in which 2 to 16 ug were added to cabbage samples showed recoveries of 101 to 120% at 2 to 4 ug for α-BHC and 2 to 8 ug for lindane and β-BHC, and recoveries of 95 to 116% for p,p'-000 and p,p'-OOT at 8 to 16 ug. Heptachlor, phorate, and methyl trithion showed low recoveries which increased to 67 to 76% recovery at 16 ug added. Other pesticides (aldrin, p,p'-DDE, dieldrin, o,p'-DDD, o,p'-DDT, diazinon, and malathion) showed from 140-318% recovery, indicating more research is needed on the quantitation of these pesticides in cabbage by GLC-ECD using an internal standard.