DIN EN ISO 20236 Water quality — Determination of total organic carbon (TOC), dissolved organic carbon (DOC), total bound nitrogen (TNb) and dissolved bound nitrogen (DNb) after high-temperature catalytic oxidative combustion

DIN EN ISO 20236 specifies a standardized procedure for the determination of total organic carbon (TOC), dissolved organic carbon (DOC), total bound nitrogen (TNb), and dissolved bound nitrogen (DNb) in various water matrices, including drinking water, surface water, groundwater, seawater, wastewater, and leachates. The method is based on high-temperature catalytic combustion followed by detection using automated instrumentation. The standard provides detailed guidance on sample preparation, calibration, quality control, and interference management to ensure accurate and reproducible results. It also includes an annex for the determination of volatile organic compounds by a difference method.

The parameters addressed in DIN EN ISO 20236 are critical indicators of water quality and environmental health. Organic carbon fractions (TOC and DOC) reflect the presence of natural organic matter and anthropogenic pollutants, influencing processes such as microbial growth, disinfection by-product formation, and overall chemical stability of water systems. Similarly, bound nitrogen species (TNb and DNb) are essential for assessing nutrient loads, which have direct implications for eutrophication and ecological balance in aquatic environments. The high-temperature catalytic combustion method ensures complete oxidation of organic and nitrogenous compounds, providing a robust and precise approach for comprehensive water quality assessment. It explicitly describes the QC measurement of a cellulose test suspension as proof for particle handling capabilities of the utilized TOC/TNb analyzer for particle loaded surface and wastewater sample matrices.

The standard DIN EN ISO 20236 is recently gaining more and more importance. In the amendment to the Water Regulation in the Netherlands, the Waterregeling (Notification Number 2025/0395/NL), it is stipulated that for the analysis of wastewater samples intended for discharge into surface waters, the TOC method (Total Organic Carbon) is explicitly required by January 2026. The regulation refers to the standard EN ISO 20236:2024 – with the clear intention of moving away from COD methods.

With the multi N/C x300 series, Analytik Jena offers a powerful and reliable standard solution for TOC/DOC and TNb/DNb analysis. The device series not only meets the requirements of DIN EN ISO 20236, it also fulfills the requirements of DIN EN 1484, DIN EN 12260 and DIN EN 15936.

Sources

• DIN EN ISO 20236 - Water quality — Determination of total organic carbon (TOC), dissolved organic carbon (DOC), total bound nitrogen (TNb) and dissolved bound nitrogen (DNb) after high-temperature catalytic oxidative combustion