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Updated: Aug 25, 2026

Analytical Techniques for Assaying Nitric Oxide Bioactivity
Published on: June 18, 2012
[Analysis of nitrites and nitrates (Unox) in urine]
Abstract:
Nitrite (NO2) and nitrate (NO3) concentrations are usually measured as a marker of NO metabolism. The aim of this study was to validate and standardize a method for the quantification of these two metabolites (nitrite and nitrate) in urine. The sample (urine) were deproteinized with NaOH, zinc sulfate and reduced with cadmium granules. Analytical recovery of NO3 added to urine samples after reduction with cadmium granules was 96-105% (Griess reaction). Calibration curves for nitrite and nitrate were linear over the concentration range of 2.1 to 200 micromole/L in urine. The detection limit of the assay was 0.9 micromole/L and the quantification limit was 2.1 micromole/L. Usual values were determined for healthy subjects: the mean concentration of NO2/NO3 (Unox) was 51.1 +/- 5.3 micromole/mmol creatinine (mean +/- SEM) (n = 15). Within-run precision was 6.6% and between-day precision was 2.2%.
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