A Rapid, Simple Spectrophotometric Method for Simultaneous Detection of Nitrate and Nitrite

Numerous methods are available for measurement of nitrate (NO−3). However, these assays can either be time consuming or require specialized equipment (e.g., nitrate reductase, chemiluminescent detector). We have developed a method for simultaneous evaluation of nitrate and nitrite concentrations in a microtiter plate format. The principle of this assay is reduction of nitrate by vanadium(III) combined with detection by the acidic Griess reaction. This assay is sensitive to 0.5 μM NO−3 and is useful in a variety of fluids including cell culture media, serum, and plasma. S-Nitrosothiols and l-arginine derivatives were found to be potential interfering agents. However, these compounds are generally minor constituents of biological fluids relative to the concentration of nitrate/nitrite. This report introduces a new, convenient assay for the stable oxidation products of nitrogen oxide chemistry in biological samples.