This standard specifies methods for the determination of: - orthophosphate (see clause 3) - orthophosphate after solvent extraction (see clause 4) - hydrolysable phosphate plus orthophosphate (see clause 5) - total phosphorus and total phosphorus after decomposition (see clauses 6 and 7). The methods are applicable to all kinds of water including seawater and effluents. Phosphorus contents within the range of 0,005 mg/l to 0,8 mg/l may be determined in such samples without dilution. A solvent extraction procedure allows smaller phosphorus concentrations to be determined with a detection limit of about 0,0005 mg/l. See annex B for some known interferences. There may be others and it is recommended to verify whether any such exist and take action to remove them.