The study is based on the water analysis CODMn in which the assay of organic compound is measured. Sweden has a standard method but the European Union has delivered a different standardised method which Swedish laboratories are suppose to use. The EU method was started up and a comparison between the two standards were performed. As a parallel study several steps of the Swedish standard were applied on the EU standard. The purpose was to determine if the best of the two methods could be combined to create a new. It was of great importance that it did not differ from the European standard by significance. The standard methods can not be considered as equivalent to each other. It is not recommended to change to the European standard immediately in spite of the higher precision, due to the increased danger in the working environment for example. Several factors of the Swedish standard method can however be applied on the European without effecting the results with any significance.