EPA 415.3 Determination of Total Organic Carbon and Specific UV Absorbance at 254 nm in Source Water and Drinking Water

EPA 415.3 specifies the method for the determination of total organic carbon (TOC), dissolved organic carbon (DOC), and specific UV absorbance (SUVA) in source water and drinking water. This method involves the oxidation of organic carbon in the water sample to carbon dioxide (CO₂), which is then measured using a detection system. The method is applicable to a wide range of water types and can detect TOC concentrations as low as 0.02 mg/L.

The relevance of measuring these parameters lies in their importance as indicators of water quality. TOC and DOC represent the amount of organic matter present in water, which can originate from natural sources such as plant and animal material, as well as from human activities such as wastewater discharge and agricultural runoff. High levels of TOC can lead to the formation of disinfection by-products during water treatment, which can pose health risks. The specific UV absorbance at 254 nm (SUVA) is used to assess the aromatic content of organic matter, which is related to its reactivity and potential to form disinfection by-products. The methods outlined in EPA 415.3, including high temperature catalytic combustion and UV-promoted chemical oxidation, provide reliable and accurate means of quantifying TOC, DOC, and SUVA levels in various water samples. This ensures compliance with environmental regulations and protects public health.

The high temperature catalytic combustion process involves heating the water sample to temperatures typically above 680°C in the presence of a catalyst, which facilitates the complete oxidation of organic carbon to CO₂. The CO₂ produced is then measured using an infrared detector, which provides a direct measure of the TOC concentration in the sample. The UV-promoted wet chemical oxidation method involves the use of a persulfate solution to oxidize organic carbon under UV light, with the resulting CO₂ measured by a conductivity detector or nondispersive infrared detector. 

To determine the SUVA, the UV absorption at 254 nm must first be determined. After filtering the water sample through a 0.45 µm membrane filter, the spectrophotometric absorbance measurement is carried out at 254 nm. For the measurement, the filtered water sample is measured against a reference sample (distilled water). The specific UV absorption is calculated using the DOC and UVA value according to the following formula:

The  accuracy and reliability of these methods are crucial for ensuring that water quality assessments are thorough and that appropriate measures can be taken to manage and mitigate organic contamination.

With the multi N/C x300 series Analytik Jena offers a range of high-quality and reliable TOC analyzers following either the high-temperature catalytic oxidation or the UV/wet-chemical sample digestion principle combined with sensitive and selective CO2 quantification by NDIR (non-dispersive infrared) detection principle. The devices not only meet the requirements of the US EPA 415.3, but also fulfill the requirements of APHA SM 5310, US EPA 9060 or ASTM D7573. In addition to the above-mentioned sum parameters also TNb can be determined fully simultaneously according to ASTM D8083 or APHA SM 4500-N E.

The SPECORD PLUS series includes UV/Vis instruments of outstanding precision and reliability, intuitive operation with a user-friendly and powerful software, and a very broad range of accessories. Whether routine analysis or complex applications, both UV/Vis novices and experts can easily achieve consistent and reproducible measurement results of highest quality. The SPECORD PLUS series offers the flexibility and ease-of-use to meet current and future analytical challenges.
 

Sources

• EPA 415.3 - Determination of Total Organic Carbon and Specific UV Absorbance at 254 nm in Source Water and Drinking Water