Rapid determination of fungicide contaminated on tomato surfaces using the DESIR-NIR: a system for ppm-order concentration

A system for rapid fungicide determination using near infrared spectroscopy was developed using the dry-extract system for infrared (DESIR) technique. Glass microfibre filter paper was used as the substrate. Fungicide solutions were prepared by dissolving the commercial dichlofluanid-carrying fungicide, Euparen, into acetone at concentrations of 2 ppm to 90 ppm of the active ingredient. Some techniques for adding the fungicide solutions onto the filter paper were examined. It was found that by adding 2mL of the fungicide solution to the filter paper held in an identical size Petri dish made of polysyrene, a sufficiently accurate calibration result with SEP of 6.58 ppm could be obtained. In the following step, the technique was applied to the determination of fungicide on tomato surfaces. The fungicide was extracted from the fruit by washing with acetone. Then, the acetone solution was used for the DESIR embedding instead of the fungicide solution in the first experiment. A satisfactory result, with an SEP of 7.89 ppm for the washed solution that was equivalent to approximately 1.58 ppm per gram fruit weight, could be obtained.