Validation of a Horizontal Standard for the Determination of Kjeldahl Nitrogen in Soils, Sludge and Treated Biowaste in a European Intercomparison Exercise

Abstract

Project HORIZONTAL is interdisciplinary aiming at a harmonisation and horizontal standardisation of test procedures, in particular for sludge, soils and biowastes. In the context of this standardization project, a series of draft technical specification were designed upon an extensive desk study, fine-tuned after expert consultations and finally validated in international intercomparisons exercise. This report summarises the work performed within the validation study of the draft standard for the determination of Kjeldahl nitrogen in soils, sludge and treated bio-waste. It further explains the underlying statistical concept for the calculation of reproducibility and repeatability from intercomparisons data. In addition all single values, results of the statistical evaluation as well as background information on the validation materials used are described and explained.