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This is the fourth in a series of laboratory proficiency exercises funded by the Agency (previously MAFF) for the measurement of radionuclides in food. Recent observations of high levels of organically bound tritium (OBT) in marine biota in the Severn estuary made fish (plaice) an obvious sample choice for this exercise. Milk was also selected since it is one of the most commonly monitored materials in the foodchain and has been used as a sample material in previous exercises.
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Tritiated thymidine was selected as the spike material since its complex combustion characteristics would give an added degree of difficulty for those laboratories that use furnace-based analytical procedures (because the high temperature might drive off some of the substances to be analysed).
Dried fish and milk samples were sourced from reputable suppliers and checked for ambient levels of tritium. The materials were spiked with tritiated thymidine, freeze-dried and homogenised. The materials were sub-sampled and an independent sub-contractor made homogeneity checks. The materials were then distributed to UK laboratories for analysis. The results were returned to the Agency, which made the results anonymous before returning them to the contractor for completion of the report.
<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>.