ISO 15681-2:2003 specifies CFA methods for the determination of orthophosphate in the mass concentration range from 0,01 mg/l to 1,00 mg/l P, and total phosphorus in the mass concentration range from 0,10 mg/l to 10,0 mg/l P. The method includes the digestion of organic phosphorus compounds and the hydrolysis of inorganic polyphosphate compounds, performed either manually as described in ISO 6878 or with an integrated UV digestion and hydrolysis unit.

ISO 15681-2:2003 is applicable to various types of water (such as ground, drinking, surface, leachate and waste water). The range of application may be changed by varying the operating conditions.

This method is also applicable to the analysis of seawater, but with changes in sensitivity, by adaptation of the carrier and calibration solutions to the salinity of the samples.