The Griess Reagent System measures nitrite (NO²⁻), which is one of two primary stable and non volatile breakdown products of nitric oxide (NO).

• Assay uses diazotisation reaction
• Based on a chemical reaction that uses sulphanilamide and N-1-naphthylethylenediamine dihydrochloride (NED) under acidic conditions
• Nitrite sensitivity dependent on matrix

Nitric oxide is an important physiological messenger and effector molecule in many biological systems including immunological, neuronal, and cardiovascular tissues. This system detects NO²⁻ in a variety of biological and experimental liquid matrices such as plasma, serum, urine, and tissue culture medium.