Multi- and univariate interpretation of the interlaboratory validation of PrEN 12673; GC determination of chlorophenols in water Original Research Article

In order to validate the (preliminary) CEN method PrEN 12673 “Water quality – Gas Chromatographic determination of some selected chlorophenols in water” an interlaboratory study was organised. The intercomparison study comprised a total of nine samples; a high-level, a low-level and a blank sample of three types of water; drinking water, surface water and waste water. The level of the spikes were based on the water quality objectives. The variation in the samples due to homogeneity and stability of the components was tested extensively and appeared to be negligible in comparison with variation between the results of the participants. Results were received from 24 laboratories from eight European countries. In this data set about 7% of the data were detected as statistical outliers and were subsequently rejected. For the remaining data set the relative standard deviations for repeatability varied between 5% and 25% and reproducibility between 26% and 56%. Both these ranges complied with the general variation in interlaboratory studies as found by Horwitz.