Swimming pool water needs to be thoroughly disinfected and this is often accomplished with ozonization. This process can generate harmful oxyhalides, the concentration of which must be monitored. Here the separation and determination of oxyhalides as well as standard anions are carried out using a column of the Metrosep A Supp 5 - 250/4.0 type. Quantification takes place using conductivity detection in accordance with sequential suppression.