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Measuring Nitrite and Nitrate, Metabolites in the Nitric Oxide Pathway, in Biological Materials using the Chemiluminescence Method
Published on: December 25, 2016
Understanding and eliminating iron interference in colorimetric nitrate and nitrite analysis.
Benjamin P Colman1, Joshua P Schimel
1University of California, Santa Barbara, CA, USA. colmanb@gmail.com
Environmental Monitoring and Assessment
|June 5, 2009
Summary
Accurate nitrate (NO_3(-)) measurements are crucial for understanding nitrogen cycling. A common analysis method is inaccurate with high soluble iron, but replacing ethylenediaminetetraacetic acid (EDTA) with diethylenetriaminepentaacetic acid resolves this interference.
Area of Science:
- Environmental science
- Analytical chemistry
- Ecology
Background:
- Nitrate (NO_3(-)) is a key nutrient for aquatic and terrestrial ecosystems.
- Accurate nitrate measurements are vital for studying nitrogen cycling.
- A common colorimetric method for nitrate analysis is susceptible to interference from soluble iron.
Purpose of the Study:
- To identify the cause of iron interference in nitrate analysis.
- To evaluate alternative buffers for the nitrate determination method.
- To recommend a modified method for accurate nitrate quantification in iron-rich waters.
Main Methods:
- Investigated iron interference in a standard nitrate analysis method using copperized cadmium reduction and diazotization.
- Tested three historical buffer systems as alternatives to ammonium chloride (NH(4)Cl) and ethylenediaminetetraacetic acid (EDTA).
- Evaluated the efficacy of diethylenetriaminepentaacetic acid (DTPA) as a replacement for EDTA.
Main Results:
- Iron interference was found to be specific to the NH(4)Cl/EDTA buffer system.
- Hypothesized iron-catalyzed reduction of a diazonium intermediate causes the interference.
- Diethylenetriaminepentaacetic acid (DTPA) effectively replaced EDTA without causing iron interference.
Conclusions:
- The presence of soluble iron interferes with accurate nitrate measurements using the common NH(4)Cl/EDTA buffer.
- Replacing EDTA with DTPA in the buffer system eliminates iron interference.
- The modified method provides accurate nitrate quantification in iron-rich aquatic and terrestrial environments.
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