A Simple Colorimetric Screening of Nitrite Using Iodide in an Acidic pH Solution

Nitrite (NO2-) is a hazardous chemical often coupled with food sample as a preservative. Azo dye based colorimetric nitrite detection approaches were quite commonly reported method for colorimetric nitrite analysis. Unfortunately, the above one found to has serious interferences from amine, carboxylic, thiol and carbonyl functional group bearing organic compounds. Here in we found a selective formation of colored product when milli-molar solution of nitrite is reacted with equal concentration of iodide in an acid pH<3. No such coloration was noticed if the iodide is coupled with various biochemicals such as ascorbic acid, citric acid, catechol, cysteine, dopamine, glucose, thiourea, urea and industrial compounds such as nitrite, nitrate, sulfide and chloride. Basic mechanism was probed by using cyclic voltammetry. Iodine was liberated upon the reaction of nitrite with iodide that showed a reddish-yellow colored solution for further nitrite screening. Finally, a simulated fish real sample analysis for screening of nitrite was successfully demonstrated.