DETERMINATION OF ORGANOPHOSPHATE INSECTICIDES IN FRESH AND DRIED PRICKLY PEAR CACTUS PADS

Abstract

The objective of this study was to identify and quantify the organophosphate insecticides in fresh and dried prickly pear pads (Opuntia ficus indica), by using the dispersive solid-phase extraction method followed by gas chromatography. Sampling was carried out at six prickly pear orchards near Hermosillo city, Sonora, México. A survey was done to know the field management regarding to the application frequency of the different insecticides, the total area sprayed, number of plant treated with insecticides, as well as planting and harvesting dates. The organophosphate insecticides analyzed were: malathion, methyl parathion, diazinon and chlorpyrifos. The calculated recovery percentage of the extraction protocol ranged from 90 to 96 % with a coefficient of variation of 12 %. Out of the 24 samples evaluated, 60 % contained three of the insecticides, whereas in the remaining samples all four insecticides were found. Malathion was found in 97 % of the samples although its concentration was within the maximum residue limits (MRLs) for vegetables. Additionally, two insecticide residues not authorized for vegetables (chlorpyrifos and methyl parathion) were detected. No insecticide residues were detected in dehydrated prickly pear pads. In samples of fresh prickly pear pads, the concentrations of malathion, methyl parathion, diazinon and chlorpyrifos were found to be below the acceptable daily intake level. It is concluded that the potential toxicological risk related to the consumption of fresh prickly pear pads and its dehydrated product is minimal because the estimated daily ingestion is 1000 times lower than the admissible dose.