Measurement of Organochlorines in Effluents (AOX and EOX)
A common practice in environmental management is to use surrogate parameters when assessing or regulating water quality. Such parameters are used when the complexity of the effluent precludes the identification and quantitation of individual chemical compounds. In the context of the chlorine issue, two surrogate parameters have been developed and have been used, or proposed for use, in regulations. The Adsorbable Organic Halogen (AOX) method determines the quantity of chlorine in a sample which is retained on activated carbon. It is viewed as determining the total quantity of organically bound chlorine. The Extractable Organic Halogen or chlorine (EOX or EOCl) method involves extraction of the aqueous sample with a non-polar solvent. The EOX test is regarded as giving a better indication of potential for bioaccumuiation than AOX and typically gives a concentration of a few percent of the AOX value (Axegård, 1986a; 1986b, Earl and Reeve, 1989) implying that most of the AOX material is hydrophilic, i.e. it is not hydrophobic.