ionexchange chromatographic analysis of peroxynitric acid ionexchange chromatographic analysis of peroxynitric acid o2nooh was performed by combining an acidic eluate with an uvvis detector and immersing the separation column in an icewater bath the decomposition behavior of peroxynitric acid in the solution was also studied using this system the fraction for the peroxynitric acid peak was collected ionexchange chromatographic analysis of this fraction after standing at room temperature for 24h showed that the decomposition products were mainly nitrate ions with a very small amount of nitrous acid the peroxynitric acid peak area correlated perfectly with the total amount of decomposition products the ionexchange chromatographic isolation allowed us to evaluate the molar extinction coefficient of peroxynitric acid precisely in a wider wavelength range than previous reports the value decreases monotonically from 172926m1cm1 at 200nm to 12005m1cm1 at 290nm