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Abstract.The element specific detection of the adsorbable organic halogen (AOX) parameter in waters has been investigated by adsorption of the halogenated analytes on activated carbon, incineration to yield carbon dioxide and hydrogen halide, trapping of the halide on a 0.01 M sodium hydroxide solution and online introduction of the halogen formed by continuous oxidation into a microwave induced plasma (MIP). Detection has been carried out by optical emission spectrometry (OES) in the visible spectral region.The performance of three microwave cavities for MIP-OES running at atmospheric pressure (Beenakker, Surfatron and Microwave Plasma Torch) as well as a reduced pressure Surfatron were investigated for halide analysis. The Surfatron device operated at 30 torr provided the best detection limits: 3 ng.m1-1 for chloride and 8 ng.m1-1 for bromide; consequently, it was the plasma chosen for AOX analysis.On-line continuous oxidation of organic compounds using KMnO4 in H2SO4 medium and in batch catalytic dechlorination with a Fe/Pd system were investigated as alternatives to the incineration method for the destruction of organic halogens to render inorganic halides are also investigated.Finally, the optimized method has been applied successfully to the determination of organochloride and organobromide in spiked river waters, being the recoveries in the interval 92-105%.Key words: adsorbable organic halogen, chloride, bromide, microwave induced plasmas, optical emission spectrometry. * To whom correspondence should be addressed Halogenated organic compounds are mostly toxic and, particularly aromatic organohalides, are among the most dangerous existing compounds as they are hardly biodegradable and accumulate in the fat tissue of animals and men.The adsorbable organic halogen (AOX) parameter has been accepted to assess the total amount of organically bound chlorine, bromine and iodine in water, expressed as micrograms of chloride per liter [1,2]. Notwithstanding the fact that AOX values do not give a detailed information about the toxicity of the analysed water, the determination of AOX is a relatively simple way for screening of organohalogenated contamination of waters. Therefore, in most European countries and in the United States limiting values of AOX have been introduced into environmental legislation. For example, in Germany the AOX is a taxable parameter for residual water since 1990 with a threshold value of 100 ng.m1-1 as chloride and procedures are laid down in the DIN norms [3].The conventional AOX method consists of three steps: preconcentration, ,combustion and detection. During preconcentration, organic material dissolved in water is adsorbed on activated carbon (AC) and thus preconcentrated and separated from inorganic halides. Then, the AC with the adsorbed organic material is introduced into a furnace and carbon is pyrolized under an oxygen-gas-flow at a temperature of at least 950 ~ to carbon dioxide. Organic halogens yield eventually hydrogen halide (HX). During the last step HX is transported by a ...