How is testing carried out?
The monitoring programme involves sampling of imported and domestic produce. Samples are taken by sampling officers of the various divisions (PRCD, Veterinary Medicines Division, Dairy Control & Certification, and Feedingstuffs, Fertilisers, Grain Marketing, Pigs & Poultry Division). The sampling officer takes a sample (e.g. of fruit) and makes a note of the grower, country of origin, date etc.
Within particular commodity groups, samples are taken at random, primarily at wholesale level or point of collection. This approach ensures that the samples taken are representative of consumption patterns and allows action to be taken, where necessary, prior to distribution. Animal fat sampling is done at factory level. Sampling is biased in favour of food items of greater dietary importance and items which have historically been found to contain pesticide residues.
Once the sample arrives in the laboratory, it is entered into the laboratory’s sample reception system. Sample analysis for pesticide residues can be broken up into a number of steps:
- Samples are chopped and frozen
- Homogenisation (normally cryogenically for fruit and vegetables)
- Sample extraction and clean-up
- Reporting of results to customers
Samples are run in batches and in general multi-residue methods (MRM’s) are used to maximise the efficiency of the analysis. For example, the current MRM for fruit and vegetables involves the analysis of each sample by both GC-MS/MS and LC-MS/MS for a scope of ~460 pesticides and metabolites.
Some pesticides are not amenable to MRM’s and they must be analysed using single residue methods (SRM’s). In this case the scope of the method covers a very limited number of pesticides and metabolites and thus is much less efficient in terms of resources.
The results are compared with the maximum residue levels (MRLs) set in EU legislation. Where there is an exceedence of the MRL, enforcement action is taken.