Measurement uncertainty for the determination of the inhibitory effect on Vibrio fischeri: a practical approach

The 11348-3:2007 ISO method allows the evaluation of the inhibitory effect of water samples on the lightemission of Vibrio fischeri; it is essential to quantify the measurement uncertainty, but there is noavailable guideline. The aim is to come up with a practical approach to calculate the measurementuncertainty. We propose a test with different 3,5-dichlorophenol dilutions to evaluate if the luminometeris functioning properly and, after, we suggest to consider the uncertainty contributions sum (xi), tocalculate the standard deviation of reproducibility (SR) and, finally, to express the expanded uncertaintywith the formula U = 2SR + u(xi).