Qualitative and quantitative determination of nitrite and nitrate with ion chromatography

Reactions of nitrogen monoxide and peroxynitrite often yield nitrite and nitrate as stable end products. The simultaneous detection of these two ions by anion chromatography with conductivity detection is described. The chromatographic system used is similar to conventional isocratic or gradient high-performance liquid chromatography equipment. The columns are packed with ion-exchanging resins instead of silica-derived adsorbents. Conductivity, though inherently nonspecific, has the advantage of covering a linear dynamic signal range of five orders of magnitude, which is far better than spectroscopic techniques; these are generally limited to two orders of magnitude. Typical run times per chromatogram are 15-30 min, and sample and standard concentrations can be between 100 nM and 10 mM. Injection volumes vary from 5 to 200 microl. Unlike with the Griess method, which determines only nitrite, a true mass balance from independent signals can be obtained if nitrate and nitrite are the only products.