Since every work step is defective, the result of an analytical method including sample preparation exhibits a certain measurement uncertainty. To be aware of measurement uncertainty is for instance very important for threshold appraisal or for industrial processes, in which only a little deviation from the nominal value is permitted. For this purpose synthetic residual waste samples were prepared through several preparation steps in order to test those samples afterwards for different chemical parameters. With the aid of the obtained data from the chemical analyses of the synthetic residual waste samples the measurement uncertainty of the overall method as well as the preparation-part of the overall measurement uncertainty was estimated for the parameters loss on ignition, total carbon and iron content. The gained results showed that an increasing number of work steps of a certain analytical method increases the value of the measurement uncertainty of this method as well. Furthermore, the obtained data indicated that the reproducibility of a method had a wide influence on the estimated measurement uncertainty. Finally, the now available measurement uncertainty data of the different analytical methods were used to make recommendations on how to lower measurement uncertainty and optimise the method. The measurement uncertainty was not estimated for the remaining parameters ash content, calorific value, content of several metals as well as content of chlorine and sulfur but a basic concept for a prospective estimation was done.