ASTM D7573-18

5.1 This test method is used for determination of the carbon content of water from a variety of natural, domestic, and industrial sources. In its most common form, this test method is used to measure organic carbon as a means of monitoring organic pollutants in industrial wastewater. These measurements are also used in monitoring waste treatment processes.

5.2 The relationship of TOC to other water quality parameters such as chemical oxygen demand (COD) and total oxygen demand (TOD) is described in the literature.1.1 This test method covers the determination of total carbon (TC), inorganic carbon (IC), total organic carbon (TOC), dissolved organic carbon (DOC), and non-purgable organic carbon (NPOC) in drinking water, groundwater, surface water, wastewater, and seawater in the range from 0.5 mg/L to 50 mg/L. Concentrations of 50–4000 mg/L of carbon may be determined by automated injection of less sample volume or by sample dilution. Alternatively, use less sample volume and calibrate at higher concentrations..

1.2 The sample is injected into a tube heated at ≥680ºC. The sample converts into a gaseous phase and forced through a layer of catalyst ensuring conversion of all carbon containing compounds to CO_{1.3 For TOC and DOC analysis a portion of the sample is injected to determine TC or dissolved carbon (DC). A portion of the sample is then acidified and purged to remove the IC. The purged inorganic carbon is measured as TIC, or DIC. TOC or DOC is calculated by subtracting the inorganic fraction from the total carbon:}

1.4 For NPOC analysis a portion of sample is acidified and purged to remove IC. The purged sample is then injected to determine NPOC.

1.5 This test method is applicable to the matrices and concentrations validated in the inter-laboratory study. It is the user's responsibility to ensure the validity of this test method for waters of untested matrices and different concentration ranges.

1.6 This test method is applicable only to carbonaceous matter in the sample that can be introduced into the reaction zone. The syringe needle or injector opening size generally limits the maximum size of particles that can be so introduced.

1.7 In addition to laboratory analyses, this test method may be applied to stream monitoring.

1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.