Sensitive Detection of Nitrite and Nitrate in Seawater by 222 nm UV-Irradiated Photochemical Conversion to Peroxynitrite and Ion Chromatography-Luminol Chemiluminescence System.

Sensitive detection methods for nitrite (NO) and nitrate (NO) ions are essential to understand the nitrogen cycle and for environmental protection and public health. Herein, we report a detection method that combines ion-chromatographic separation of NO and NO, on-line photochemical conversion of these ions to peroxynitrite (ONOO) by irradiation with a 222 nm excimer lamp, and chemiluminescence from the reaction between luminol and ONOO. The detection limits for NO and NO were 0.01 and 0.03 μM, respectively, with linear ranges of 0.010-2.0 and 0.10-3.0 μM, respectively, at an injection volume of 1 μL. The results obtained by the proposed method for seawater analysis corresponded with those of a reference method (AutoAnalyzer based on the Griess reaction). As luminol chemiluminescence can measure ONOO at picomolar concentrations, our method is expected to be able to detect NO and NO at picomolar concentrations owing to the high conversion ratio to ONOO (>60%), assuming that contamination and background chemiluminescence issues can be resolved. This method has the potential to emerge as an innovative technology for NO and NO detection in various samples.