Tri-iodide and vanadium chloride based chemiluminescent methods for quantification of nitrogen oxides

Nitric Oxide (NO) is an important signaling molecule that plays roles in controlling vascular tone, hemostasis, host defense, and many other physiological functions. Low NO bioavailability contributes to pathology and NO administration has therapeutic potential in a variety of diseases. Thus, accurate measurements of NO bioavailability and reactivity are critical. Due to its short lifetime in vivo and many in vitro conditions, NO bioavailability and reactivity are often best determined by measuring NO congeners and metabolites that are more stable. Chemiluminescence-based detection of NO following chemical reduction of these compounds using the tri-iodide and vanadium chloride methods have been widely used in a variety of clinical and laboratory studies. In this review, we describe these methods used to detect nitrite, nitrate, nitrosothiols and other species and discuss limitations and proper controls.