What causes the Nitrate and Nitrite Test Strips to change color?
Color change on Nitrate and Nitrite Test Strips
The pad on the Nitrate and Nitrite Test Strips (Product # 2745425) contains a metal reducing agent that will reduce the Nitrate to Nitrite. Once reduced to nitrite, under acidic conditions, the sample will diazotize with an aromatic amine (sulfanilamide). This diazo compound will then couple with another aromatic amine (1,2,3,4-Tetrahydro-benzo[h]quinolin-3-ol (HTBQ)) which produces a pink-violet color used to indicate the concentration of Nitrate and Nitrite. This reaction is a modified Griess Reaction.