NEMI Method Summary

Method Summary Information

Method Number: D5997 Media: WATER
Revision: Reapproved 2000. Current edition approved July 10, 1996.
Method Source: ASTM International
Subcategory: ORGANIC Analytes in this method
Official Name: Standard Test Method for On-Line Monitoring of Total Carbon, Inorganic Carbon in Water by Ultraviolet, Persulfate Oxidation, and Membrane Conductivity Detection
Descriptive Name Carbon (all forms), On-Line Measurement in Water
Source Info: ASTM International
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Conshohocken, PA 19428
Telephone: (610) 832-9500
Fax: (610) 832-9555
Email: service@astm.org
Citation: ASTM Volume 11.01
 
Brief Method
Summary:
 Carbon can occur in water as inorganic and organic compounds. This test method can be used to make independent measurements of IC and TC and can also determine TOC as the difference between TC and IC. If IC is high relative to TOC, it is desirable to use a vacuum degassing unit to reduce the IC concentration to obtain meaningful TOC values by difference.
The basic steps of this test method are:1) Conversion of remaining IC to CO2 by action of acid, 2) Removal of IC, if desired, by vacuum degassing, 3) Split of flow into two streams to provide for separate IC and TC measurements, 4) Oxidation of TC to CO2 by action of acid-persulfate aided by ultraviolet (UV) radiation in the TC channel, 5) Detection of CO2 by passing each liquid stream over membranes that allow the specific passage of CO2 to high-purity water where change in conductivity is measured, and 6) Conversion of the conductivity detector signal to a display of carbon concentration in parts per million (ppm = mg/L) or parts per billion (ppb = ug/L). The IC channel reading is subtracted from the TC channel reading to give a TOC reading.
Scope And
Application:
 This test method covers the on-line determination of total carbon (TC), inorganic carbon (IC), and total organic carbon (TOC) in water in the range from 0.5 g/L to 50 000 g/L of carbon.
Applicable
Conc Range:
 0.5-50,000 ug/L
Interferences: The oxidation of dissolved carbon to CO2 is brought about at relatively low temperatures by the chemical action of reactive species produced by UV-irradiated persulfate ions. Not all suspended or refractory material may be oxidized under these conditions.
Other interferences have been investigated and found to be minimal under most conditions. The membrane is hydrophobic in nature and passes only gaseous materials. Potential interferences are nitrite, sulfide, and high levels of hypochlorite or iodine.
Use of the vacuum degassing unit or sparging the sample renders the IC reading meaningless and may cause loss of volatile organic compounds, thus yielding a value lower than the true TOC level. At low TOC levels, the degassing unit may introduce a measurable TOC and IC background.
QC Requirements: Instrument calibration must be performed according to the manufacturer's schedule and instructions.
Instrument calibration and blank readings must be checked whenever reagents or UV lamps are changed. The calibration check should be carried out with a different calibration material and concentration than that used for the instrument calibration.
Resin quality should be checked at the same frequency as UV lamp replacement. In the on-line mode with the UV lamp off, measure low TOC water (< 100 mg/L) that has been deionized to a resistivity of > 18 Mohm-cm. If either the TC or IC channel measures > 10 ug/L, the resin may need replacement.
The user should confirm that the unit is giving proper response using the sample matrix with compound types of interest and operating under the environmental extremes of interest.
Sample Handling: Collect the sample in accordance with Specification D 1192 and Practices D 3370.
Max Holding Time:
 
Relative Cost: Unknown
URL to obtain ordering information for this method:
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