International N-nitrosamine check sample programme: report on the performance in the 1st study dedicated to determination of N-nitrosamines in beer and malt.

Two samples, one beer and one malt, have been distributed to 55 laboratories in 15 countries, to be analysed for N-nitrosodimethylamine (NDMA) N-nitrosopyrollidine (NPYR) and N-nitrosoproline (NPRO) by the method of their choice. Results received from 35 laboratories demonstrated that at the low levels of contamination which may be encountered at present for NDMA in beer and malt, generally reliable data can be obtained in malt, but in beer, 20% of the results were discarded as outliers by the statistical test results. More variability was encountered for the analysis of NPYR. Only a limited number of results were provided for NPRO, which also showed greater variability.