Examination of the reliability of the sum parameters AOX and EOX

The sum parameters AOX and EOX are susceptible to interferences by high amo unts of chloride ions and organic carbon (TOC). Nature and extent of these influences were determined by using model solutions containing inorganic ch loride, humic acids and halogenated organic xenobiotics, as well. As a resu lt AOX blank tests with chloride solutions (NaCl, FeCl3, CuCl2 and ZnCl2) h ave shown a dependence of the AOX value upon the nature of the cation. A co nsiderable decrease of AOX values measured was caused by coprecipitation of halogenated xenobiotics and humic acids. This was observed by using model solutions of 1,4-dichlorobenzene 2,4-dichlorophenol and 4-chloro-2-nitroani line. Humic acid solutions were halogenated in the laboratory using hypochl orite and the AOX values of these solutions were compared to the EOX values measured from the same samples. The chlorinated products were registered b y both parameters, AOX and EOX as well. Indeed the EOX values of these mode l solutions were dependent on the extraction solvent used.