Standard Test Method for Total Nitrogen, and Total Kjeldahl Nitrogen (TKN) by Calculation, in Water by High Temperature Catalytic Combustion and Chemiluminescence Detection
5.1 This test method is used for determination of the total or dissolved nitrogen content of water from a variety of natural, domestic, and industrial sources. In its most common form, this test method is used to measure nitrogen as a means of monitoring nutrient pollutant in industrial wastewater, domestic wastewater, and ambient water. These measurements may also be used in monitoring waste treatment processes.
5.2 This test method measures oxidized ammonia and organic nitrogen (as nitrate) and soluble nitrate simultaneously, subtracting the nitrate + nitrite value from a non-digested sample gives total Kjeldhal nitrogen (TKN).
When using this test method:
1.1 This test method covers the determination of total nitrogen (TN) and total dissolved nitrogen (TDN) in surface water, seawater, groundwater, wastewater, and wastewater effluents in the range from 0.2–10 mg/L N. Concentrations from 10–500 mg/L are possible when used in conjunction with manual or automatic dilution, or automatic injection of less sample volume. The EPA 40 CFR Part 136 Appendix B Method Detection Limit (MDL) is 0.05 mg/L N. Higher concentrations may be determined by sample dilution. Lower concentrations may be possible by injecting larger sample volumes. Follow the manufacturer’s instructions.
1.2 The sample is injected onto a platinum catalyst heated at ≥720ºC. The sample converts into a gaseous phase and is forced through a layer of catalyst ensuring conversion of all nitrogen containing compounds to nitrogen oxide (NO). Reaction with ozone converts the NO to an exited NO2. As the excited NO2 returns to the ground state, it emits radiation that is measured photo-electrically.
1.3 Total and dissolved organic carbon analysis by Test Method D7573 can be analyzed at the same time on the same sample simultaneously using a properly equipped analyzer. (See Appendix X1 for an example of simultaneous TOC data.)
1.4 This test method quantitatively recovers nitrogen from a large range of organic and inorganic nitrogen compounds (see Table 1 and Table 2). The test method does not measure nitrogen gas (N2). It is the user's responsibility to ensure the validity of this test method for waters of untested matrices.
1.5 This test method is applicable only to nitrogenous 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. Optional automatic sample homogenization may be used.
1.6 This test method is performance based. You may make modifications that improve the test method’s performance but do not change the oxidation or detection technique.
1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.8 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.
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