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The quality of measurements made to assess the concentration of components in food is fundamental. The decisions made by producers, vendors, consumers and the regulators of foods rely upon their accuracy. In recent years, it has been increasingly realised that an important part of the measurement process is often the sampling of the food that takes place outside the laboratory.
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In a Sampling Proficiency Test (SPT), several organisations (n=8) are required to take independent samples, and make analytical measurements, on the same sampling target. This would typically be a bulk consignment of a food material. The analytical measurments can be made by each participant (or their nominee), but the concept of the SPT is tested initially when all the chemical analyses are made in one laboratory.
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The proposed SPT on food will be the first of its kind in the world, and will provide a new tool for assessing the proficiency of samplers. This will help the individual samplers to improve their performance, and become aware of the effect of sample heterogeneity on the measurement result.
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Potentially, it will also improve the quality of sampling in the whole food sector, which has happened as a consequence of analytical proficiency tests. This will enable better international comparability of measurements, especially if future SPTs are conducted with international participation. Moreover, the results of any SPT will provide information to enable more realistic estimates of the uncertainty of measurements. This, in turn, will improve the reliability of decisions based upon the composition and contamination of foods.
A sampling target will be selected to fulfil the necessary criteria, in terms of size, analyte (considering the limit of detection, expected precision, temporal stability, and heterogeneity), availability of defined sampling protocols and common occurrence of commodity.
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It is essential to characterise the candidate sampling targets before the SPT in terms of essential characteristics (see above). In order to detect any temporal change, the target will need to be characterised for the target analyte before and after the SPT.
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Participants with relevant experience of the sampling target/analyte will be selected, given a clear description of their objective and instructions for the SPT. The instruction will clearly identify the sampling target and the participants must select whatever protocol they consider most appropriate.
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The scoring scheme will be devised in general agreement with the harmonised protocol for analytical proficiency tests (Thompson et al. for IUPAC, 2005), but adapted to the particular requirements of a SPT. Participants will be supplied with their 'score' with related comments and estimates of the measurement uncertainty.
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Comments on both the practicality and usefulness of the SPT from participants and organisers will be collated. The constraints on the selection of the sampling target and participants will be reviewed and conclusions reached as to the broad applicability of SPTs in the food sector. The usefulness to the participants will be reviewed, and compared with the perceived usefulness of analytical PTs. Lessons learnt from the initial application will be addressed in a second application of the SPT in the later stages of the research project.
<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>.