The fifth international and (Dutch) national trial with reference materials for water microbiology
Het vijfde internationale en (nederlandse) nationale ringonderzoek met referentiematerialen voor watermicrobiologie
Mooijman KA, Havelaar AH, van Strijp-Lockefeer NGWM, Heisterkamp SH
RIVM Report 148602006
Thirty-nine Dutch laboratories and 33 laboratories of the EC participated in a fifth trial with reference materials for water microbiology. Reference materials with the test strains WR63 Enterococcus faecium and WR52 Staphylococcus warneri were used. The materials were analysed for total aerobic viable bacteria by a reference method and the national standard method, both with incubation at 22 and 37 degrees C. After statistically analysing the results, the repeatability (r) and reproducibility (R) were calculated. Very good results were found for r and R. Especially the values of r found with the material with strain WR63 were very close to the theoretical optimum.