ISO 9562 Water Quality - Determination of Adsorbable Organically Bonded Halogens (AOX)

The standard "ISO 9562 Water quality - Determination of adsorbable organically bound halogens (AOX)" published by the International Organization for Standardization (ISO) describes a method for the direct determination of the amount of organically bound chlorine, bromine and iodine (expressed as chloride) adsorbable on activated carbon, typically to the extent of 10 µg/l in water. This method is applicable to test samples having inorganic chloride ion concentrations less than 1 g/l. Samples with higher concentrations are diluted before analysis.

This method can also be applied to samples containing suspended solids where the halogens are adsorbed to the solid (such as insoluble halides). Filtering the sample before analysis allows the separate determination of dissolved and particulate adsorbable organically bound halogens (AOX).

Filtered samples with high inorganic chloride content can be analyzed by a modified method (dissolved adsorbable organically bound halogens after solid phase extraction in waters with high salt content). However, the results obtained by this modified method may differ significantly from the results obtained by the desired method.

For the purposes of this standard, the following terms and definitions apply:

• Adsorbable organically bound halogens (AOX) express the equivalent amount of chlorine, bromine and iodine present in organic compounds, expressed as chlorides, when determined according to this standard.
• Dissolved organic carbon refers to the amount of organically bound carbon present in water originating from carbon.

In this standard, initiatives are described as follows:

• High AOX values ​​may be due to the presence of active chlorine and some inorganic bromine and iodine compounds irreversibly bound to the activated carbon. Reactions of these oxidizing agents with organic matter and activated carbon in the sample can be prevented by adding sodium sulfite immediately after sampling.
• Organic bromine and iodine compounds may decompose to elemental bromine or iodine, respectively, during combustion, leading to higher oxidation states of these elements. These AOX fractions may be underdetermined, leading to a negative bias.
• Samples containing living cells (e.g. microorganisms or algae) may produce high results due to their chloride content. In these cases, the sample is analyzed at least 8 hours after acidification.
• For samples with high chloride concentrations (approximately 1 g/l), the shaking procedure may cause higher interferences than the column procedure.
• Alcohols, aromatic compounds or carboxylic acids may cause a negative bias (e.g. in case of dissolved organic carbon values ​​> 100 mg/l).
• For samples containing suspended solids, the stirring method may result in inadequate coating of the particles. If the particles contain substances that contribute to AOX, the shaking or column method is recommended.
• The recovery of some polar and hydrophilic compounds such as monochloroacetic acid is incomplete.

This standard is based on the following principles:

• Acidification of the water sample with nitric acid.
• Adsorption of organic compounds present in the sample onto activated carbon by shaking procedure, mixing procedure or column adsorption.
• Displacement of inorganic halides by rinsing activated carbon with sodium nitrate solution acidified with nitric acid.
• Burning of the charged carbon in a stream of oxygen.
• Absorption of hydrogen halides in an acceptor solution followed by determination of halide ions by an argentometric titration such as microcoulometry.
• Express the result as the mass concentration of chloride.

The activated carbon adsorption device used in these tests has the following apparatus for the shaking procedure: filtration apparatus, polycarbonate membrane filter, conical flask and mechanical shaking device for flasks.

The activated carbon adsorption device has the following apparatus for mixing method: conical flask, connecting apparatus for activated carbon felt, activated carbon felt and rinsing device.

Activated carbon adsorption device has the following apparatus for column procedure: ceramic wool.

These tests also use a combustion and detection device. This device has the following apparatus: combustion apparatus, quartz vessel, argentometric measuring device, absorber and syringe.

Measuring flasks and flat-bottomed sample bottles are also used in the tests.

Our organization has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. Among the numerous test, measurement, analysis and evaluation studies provided for businesses in various sectors, there are also testing services in accordance with the standard “ISO 9562 Water quality - Determination of adsorbable organically bound halogens (AOX)”.