A field unit for determining dimethoate in fruit and vegetable dips.
Nobel A., Walsh J. J., Outhwaite R. J.
Author Affiliation: Agricultural Chemistry Branch, Department of Primary Industries, Indooroopilly, Queensland 4068, Australia.
Pesticide Science 29 : 387-395
Abstract : In order to control Queensland fruit fly, Dacus tryoni [Bactrocera tryoni], postharvest treatments with dimethoate dips are necessary before produce such as avocado, mango, tomato, capsicum and banana can be marketed interstate or internationally. The concentration of dimethoate needs to be maintained at 400 or 500 mg/litre to ensure that fruit flies are killed and also to keep residue levels below the MRL. A field unit which contains a colorimeter, a heating block and cooling positions was evaluated. The diluted dip sample produced a colour with 4-(p-nitrobenzyl)pyridine after heating and the addition of tetraethylenepentamine. Precision of the unit was acceptable for a field test (repeatability of ±10.1%) and there was reasonable agreement between determinations made on the unit and by an HPLC method for a range of dimethoate concentrations from 300 to 700 mg/litre. The unit can be used at the dip site and the analysis is completed in 30 minutes.