Stability of the standard nitric oxide solution – The changes of UV–Vis spectrum over one year

The stability of standard nitric oxide solution can be observed by UV–Vis spectrometry; it is possible to observe changes over 365 days of storage but also over one day under air-equilibrated conditions. Nitrous acid tetrad appeared after one week and disappeared after three months; the peak of nitrate ions appeared after one month and grew for the next two months, it reached the maximum when the nitrous acid tetrad disappeared, and the spectrum of nitrate ions was stable for the rest of the year.