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This research project aims to determine the effectiveness of a rapid method for analysing a range of organic chemicals from the surface of a range of fruit, leafy vegetables, wheat grain or grass.
<p>This project was designed to test the effectiveness of rapidly recovering low volatility or polar organic chemicals from the surface of intact fruit, vegetable leaves, wheat grain or grass, and analysing the extracts by MALDI-TOF MS.
<p>The initial stage of the project was to optimise the MALDI-operating conditions for nine test chemicals, using 'delayed extraction' mode, which increases resolution compared with MALDI-TOF.
<p>This involved empirical testing of the effectiveness of various matrix compounds for MALDI, combined with different solvents.
<p>Preliminary tests were then carried out to establish the approximate limits of detection for the test analytes in standard solutions containing 100, 10 and 1 microgram per millilitre.
<p>The next step was to test different solvent extraction protocols to optimise the selective efficient recovery of chemicals deposited on the surfaces of the test food samples without extracting intrinsic components from the food samples, such as wax from apple skins, that could interfere with the MALDI-TOF analysis.
<p>As MALDI sample spots have a tendency to be inhomogeneous due to the crystalline nature of the matrix material, the spectra from different spots, or different parts of a single spot can give quantitatively variable results.
<p>Therefore the final phase of this project was to devise an experimental protocol to control the variability of sample spots.
<p>The approach that was taken was to use an internal reference compound and compiling data from a large number of replicate laser shots of each test sample to provide statistical control.
Emissions from accidental, uncontrolled fires involving chemicals can contain complex mixtures of volatile and semi-volatile organic contaminants, which can be deposited onto crops or pasture beneath the smoke plume.
<p>There is a need for the development of rapid and automated methods for screening foods for the presence of a wide range of organic contaminants.
<p>This project was intended to explore the use of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) for screening organic contaminants that are polar and/or have relatively low volatility and would therefore not be amenable to headspace sampling techniques and conventional mass spectroscopy detection.
<p>Find more about this project and other FSA food safety-related projects at the <a href="http://www.food.gov.uk/science/research/" target="_blank">Food Standards Agency Research webpage</a>.