BioVision’s Nitric Oxide Fluorometric (Cat# K252-200) and Colorimetric (K262-200) Assay Kits provide an accurate and convenient measurement of total nitrate/nitrite concentration in a simple two-step process. The first step is the conversion of nitrate to nitrite utilizing nitrate reductase. For fluorometric assay, the second step involves addition of DAN followed by NaOH, which converts nitrite into a fluorescent compound. Measurement of the fluorescence of this compound accurately determines the total nitric oxide production. For colorimetric assay, the second step involves addition of the Griess Reagents which convent nitrite into a deep purple azo compound. Measurement of the absorbance of the azo chromophore accurately determines the total nitric oxide production. Both kits have been validated in culture media, plasma, and tissue homogenates. Some sample purification from these sources may be necessary.