Adsorbable organic halides (AOX) is an organic sum parameter comprising such organics that contain chlorine, bromine or iodine (not fluorine!) atoms and are adsorbable to activated carbon. For AOX determination a particular volume of the wastewater sample is agitated sufficiently long with powdered activated carbon. Subsequently the activated carbon is separated by filtration using a membrane filter which retains the activated carbon (adsorption can also be executed in small activated carbon columns which are treated - after adsorption has been completed - in the same way as the loaded activated carbon removed by filtration). Then the membrane filter is incinerated together with the activated carbon in a stream of pure oxygen at temperatures around 900°C. The halogen atoms originally bound in organics adsorbed to the activated carbon form HCl, HBr, or HI, resp., which are contained in the exhaust gas of the incineration furnace and can be absorbed e.g. in acetic acid. Microcoulometric titration, an electrochemical quantification method, analyses chloride, bromide, or iodide, resp., of these acids. Bromide and iodide are calculated as chloride equivalents (one mol bromide or iodide is looked at as one mol chloride and is calculated as chloride mass), and the final chloride mass determined is related to the volume of the wastewater sample which had been subdued to activated carbon adsorption. The result is mg AOX (chloride)/l wastewater. For details of the method, see Greenberg et al. (1985).

In the AOX analysis procedure, artefacts can easily be produced: First, also inorganic chloride adsorbs to a certain amount to activated carbon. This adsorbed inorganic chloride will also be detected e.g. by microcoulometric analysis of the incineration off-gass and may result in the so-called "chloride error". Secondly, in wastewaters with high TOC mainly represented by non-halogenated organic compounds a competition of halogenated and non-halogenated organic compounds for adsorption sites on the activated carbon occurs leading to a very low extent of halogenated organic molecules being adsorbed. This can be prevented by dilution of the wastewater sample. However, by dilution also the AOX is diluted which is disadvantageous if the AOX content of the sample is decreased to be below the detection limit of the method. AOX analyses must be performed in laboratory rooms where no halogenated organic solvents are used at all, because these volatiles would also adsorb on the activated carbon during the AOX procedure. In recent years, AOX analyses in the Institute of Wastewater Management of Hamburg University of Technology had been performed in a laboratory where a thermostatized chamber was located. When there was a leakage in the cooling system of the chamber, some fluorochlorohydrocarbons were volatilized in the laboratory leading to severe analytical errors in AOX determinations.

Other parts of organics contained in wastewaters (usually comprised in TOC or COD) are the organic sum parameters hydrocarbons, phenols, anionic surfactants, neutral surfactants, cationic surfactants etc. Methods for analyzing these organic sum parameters are also given in the "Standard Methods" (Greenberg et al. 1985).