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 2 - ) and nitrate (NO 3 - ) 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 2 - and NO 3 - , 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 2 - and NO 3 - 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 2 - and NO 3 - 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 2 - and NO 3 - detection in various samples.