UC-Davis: Nitrate via V(III) reduction: Nitrate via manual vanadium(III) reduction
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Official Method Name
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Nitrate via manual vanadium(III) reduction |
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Current Revision
| 2005 |
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Media
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WATER |
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Instrumentation
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Spectroscopy (Colorimetry; Photometry) |
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Method Subcategory
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Inorganic |
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Method Source
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Citation
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Doane, T.A., and Horwath W.R., 2003, Spectrophotometric determination of nitrate with a single reagent. Analytical Letters 36(12):2713-2722. Marcel Dekker Publishing. |
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Brief Method Summary
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Vanadium(III) in dilute acid solution effects the quantitative reduction of nitrate to nitrite and/or nitric oxide, both of which are captured by Griess reagents to produce a red dye. A single reagent solution is prepared, which may be stored indefinitely for future use. The reagent is mixed with samples directly in disposable cuvets, and absorbance read after color development. |
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Scope and Application
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The method is applicable to a wide range of sample types, including fresh and saline waters, acid and buffered solutions, and samples with high levels of dissolved organic matter. This method is applicable to the determination of nitrate in a wide range of environmental and other samples, including agricultural runoff, ocean water, wastewater, and persulfate-digested samples. |
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Applicable Concentration Range
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>0.002 ug nitrate-N/ml |
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Interferences
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High amounts (greater than about 100 ppm) of phosphate, sulfate, or dissolved organic matter may reduce the efficiency of reaction when low amounts of nitrate (less than about 0.05 ppm N) must be determined. This is dealt with by simply using more reagent relative to sample. Other interferences include high (greater than 100 ppm) amounts of oxidizing agents such as Fe(III) or chlorine, as well as substances that interfere with the Griess reaction, including ascorbate and azide. Being a spectrophotometric procedure, samples must not be turbid and should not show absorbance at 540 nm. Both of these characteristics may be corrected for or the samples may be pretreated (e.g. by filtration). |
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Quality Control Requirements
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The method presents only the procedure itself and associated validation data; no specific QC operations are addressed. They may be determined at the discretion of the analyst considering the nature of the work for which results are being generated. Other methods for nitrate determination may be consulted for detailed QC operations. Nevertheless, QC practices such as checks and matrix spikes are desirable in any sample run. |
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Sample Handling
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The method does not specifically address sample handling; this should be considered by the analyst depending on the nature of the samples and reporting requirements. Other methods may be consulted for relevant sample handling instructions. Nonetheless, it is generally advisable to begin analysis as soon as practical following receipt of samples. |
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Maximum Holding Time
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48 hours is suggested |
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Relative Cost
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Less than $50 |
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Sample Preparation Methods
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