Validation of the Dumas method for nitrogen quantification and determination of conditions of use based on its measurement uncertainty and discrimination threshold

Abstract

Many biological studies aim to reveal differences in concentration for a given analyte between individuals or between experimental treatments. To meet this objective, a suitable analytical method capable of detecting the desired differences is required. The method validation implemented in the INRAE quality policy allows to establish a measurement uncertainty curve and to calculate the discrimination threshold of analytical methods. In the work presented here, we have used these validation techniques for a method used to quantify nitrogen in wheat flour using an elemental analyser. We modelized the measurement uncertainty in three conditions based on technical repetitions i.e. by quantifying validation samples once, twice or three times. Increasing the number of technical repetitions is a way to improve the measurement uncertainty of the method and to make it able to discriminate closer measurements. The results obtained therefore allow a better knowledge of the method used. Consequently, a client can be advised objectively concerning the analyses to be carried out according to the desired level of discrimination.