This European Standard specifies a procedure for complete digestion of raw/digested sludge, suitable for the subsequent determination of phosphorus.NOTE Phosphorus in environmental samples can be present in many forms. This method of pre-treatment enables the analyst to determine all forms - i.e. total phosphorus, by quantitative oxidation yielding an aqueous solution of orthophosphate which should be analysed for phosphate according to method EN ISO 6878, EN ISO 10304-2 or an equivalent validated method.The range of the method is up to 50 g/kg P assuming appropriate dilution of the digest in the final measurement step.