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ASTM D7781-14

ASTM D7781-14

Standard Test Method for Nitrite-Nitrate in Water by Nitrate Reductase

2019-01-28 /Active
Significance and Use:

5.1 This test method replaces Test Methods D1254 (Nitrite) and D992 (Nitrate). The nitrite test method (Test Method D1254) used a reagent that is considered to be a potential carcinogen. The nitrate test method (Test Method D992) has been shown to have relatively large errors when used in wastewaters and also has greater manipulative difficulties than the test method described herein.

5.2 This test method can be used in place of Test Methods D3867 (Nitrite-Nitrate). Test Methods D3867 uses cadmium for the reduction of nitrate to nitrite. Cadmium is considered a toxic metal. Also, the heterogeneous cadmium reductant creates greater difficulty than the reduction described in this test method.


1.1 This test method is applicable to the determination of nitrate plus nitrite (as nitrogen) in drinking water, surface, saline, wastewater, and ground waters. The applicable range of this test method is from 0.05 to 5 mg/L of nitrogen. The range may be extended upward by dilution of an appropriate aliquot. The 40 CFR Part 136 Method Detection Limit (MDL) is 0.02 mg /L.

1.2 It is the user's responsibility to ensure the validity of this test method for waters of untested matrices. The quality control criteria in Section 17 for method blanks, laboratory control samples, matrix spikes and matrix duplicates must be met.

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

1.4 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.

nitrate; nitrite; nitrate plus nitrite; discrete analyzer; nitrate reductase; enzyme; cadmium reduction
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