AN INTERLABORATORY TEST FOR THE DETERMINATION OF
POLYNUCLEAR AROMATIC HYDROCARBONS (PAH) IN DRINKING WATER (EC 9504
Report No DWI0452
To provide evidence on the accuracy of analysis in 27 laboratories participating in a survey of polynuclear aromatic hydrocarbons (PAB) in drinking water.
A European Community Directive defines maximum admissible concentrations of 200 ng/l for 6 specified PAH in drinking water. The Department of the Environment has initiated a survey of current levels of PAH in drinking water in England and Vales. An assessment of the quality of data is essential to the interpretation of the survey. Interlaboratory tests are used as a means of evaluating the size of analytical errors existing in groups of laboratories.
The accuracy of PAH determination in drinking water is similar to that achieved for other trace determinands. Errors of over 40% are not uncommon.
Analytical error has serious implications for the interpretation of the results of the PAH survey. Random errors make if difficult to demonstrate compliance with a water quality standard. Systematic error in PAH determination appears to be predominantly negative. Mean bias of -20% to -30% is evident and may be associated with incomplete extraction of the determinands from aqueous solution.
IV RESUME OF CONTENTS
The experimental approach to the circulation of the two test samples for PAH determination is described. The results reported by 27 laboratories suggest that large errors can affect the determination of PAH. The overall mean result obtained by all laboratories was in reasonably good agreement with the known reference concentration, but individual results were in error by up to 90 ng/l at a nominal concentration of 120 ng/l and as much as 8 to 10 ng/l at a concentration of 10 ng/l.
Copies of this report may be available as an Acrobat pdf download under the 'Pre 2000 Reports' heading on the DWI website.