What causes the Nitrate and Nitrite Test Strips to change color?

Document ID

Document ID TE3479

Version

Version 4.0

Status

Status Published

Published Date

Published Date 09/13/2018
Question
What causes the Nitrate and Nitrite Test Strips to change color?
Summary
Color change on Nitrate and Nitrite Test Strips
Answer
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.
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