Imazalil (1-{2-(2,4-Dichlorophenyl)-2-[(prop-2-en-1-yl)oxy]ethyl}-1H-imidazole) is a post-harvest fungicide widely used for mold control in fruits and vegetables. Usually, imazalil is applied on apples in a concentration of 1000 ppm by dipping, drenching or spraying treatments and this can result in diffusion of the fungicide from the exocarp to mesocarp of the fruit. Gas chromatography and high-performance liquid chromatography mass spectrometry are techniques often used for analysis of pesticides in fruits; however, both techniques require labor intensive steps of sample preparation prior to analysis and do not provide information about the distribution of the analyte in the sample. Mass spectrometry imaging can spare laborious sample preparation and speed up analysis. Moreover, localization information from MS imaging can provide an indication of the distribution of the fungicide inside fruit. In this work, we use matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging for location analysis of imazalil in apples. Imazalil (1000 ppm) was applied to fresh organic gala apples by dip treatment for 2 min and left to dry. Samples were stored at 25 C and two apples were cut one day apart from each other into 200 µm thick sections using a vibratome and mounted on glass slide. For MALDI imaging, the apple sections were sprayed with matrix and mass spectra were acquired using a MALDI-TOF/TOF mass spectrometer in reflectron mode at a lateral resolution of 150 µm. On day 0, imazalil was detected only in the exocarp region. However, after one day the analyte was detected in mesocarp region in a ladder pattern showing that some of the imazalil migrated toward the inner region of the apple. Further experiment will be performed with longer incubation times (up to 7 days) to verify the fungicide penetration. Laser ablation extraction of regions of interests followed by ESI-MS will be used for quantification experiments.

MALDI imaging and laser ablation sampling for analysis of fungicides in produce

255th National Meeting (2018)

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