5.1 Accurate measurement of organic carbon in water at low and very low levels is of particular interest to the electronic, life sciences, and steam power generation industries.

5.2 Elevated levels of organics in raw water tend to degrade ion exchange resin capacity. Elevated levels of organics in high purity water tend to support biological growth and, in some cases, are directly detrimental to the processes that require high purity water.

5.3 In power generation, naturally occurring organics can become degraded to CO₂ and low molecular weight organic acids that, in turn, are corrosive to the process equipment. Their effect on conductivity may also cause water chemistry operating parameters to be exceeded, calling for plant shutdown. Halogenated and sulfonated organics may not be detectable by conductivity but at boiler temperatures will release highly corrosive chlorides, sulfates, etc.

5.4 In process water in other industries, organic carbon can signify in-leakage of substances through damaged piping and components, or an unacceptable level of product loss.

5.5 In wastewater treatment, organic carbon measurement of influent and process water can help optimize treatment schemes. Measurement of organic carbon at discharge may contribute to regulatory compliance.

5.6 In life sciences, control of organic carbon is necessary to demonstrate compliance with regulatory limits for some types of waters.

1.1 This guide covers the selection, establishment, and application of monitoring systems for carbon and carbon compounds by on-line, automatic analysis, and recording or otherwise signaling of output data. The system chosen will depend on the purpose for which it is intended (for example, regulatory compliance, process monitoring, or to alert the user to adverse trends) and on the type of water to be monitored (low purity or high purity, with or without suspended particulates, purgeable organics, or inorganic carbon). If it is to be used for regulatory compliance, the test method published or referenced in the regulations should be used in conjunction with this guide and other ASTM test methods. This guide covers carbon concentrations of 0.05 µg/L to 50 000 mg/L. Low end sensitivity and quantitative results may vary among instruments. This guide covers the on-line measurement techniques listed in Table 1. Additional laboratory test methods are available: Test Methods D4129, D4839, D5904, D6317, and D7573.

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

1.3 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 and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 9.