Ion mobility spectrometry of laser desorbed pesticides from fruit surfaces

The applicability of a technique combining laser desorption and ion mobility spectrometry for rapid detection of pesticides on fruit surfaces is explored. A selection of 20 fungicides, herbicides and insecticides with very different chemical and spectroscopic characteristics was used to study its features. For a variety of fruits the maximum tolerable laser irradiance was determined, at which no signals are generated by the clean surface. The spectra recorded for each substance on fruits were compared to those obtained for the same compound using laser desorption from a well defined surface. Furthermore, the influence of a dew layer on the sample was investigated. Limits of detection were estimated to be in the range of some tens of ng/kg for apples.