As
described by Fox, the color development in the selected reaction
results as a balance of the formation of HNO2, protonation of
the naphthalene derivative, and the potential decomposition of the
azo dye at lower pH values (such as 10% HCl).According to our
results, and although the pink blushing resulting from the degradation
of the Griess reagent was still evident, it was concluded that
5% H3PO4 provided the best analytical performance of the device
and was implemented in all subsequent experiments.