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

• Published in: Environmental science & technology Vol. 57; no. 14; pp. 5924 - 5933
• Main Authors: Kodamatani, Hitoshi, Kubo, Shotaro, Takeuchi, Akinori, Kanzaki, Ryo, Tomiyasu, Takashi
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 11-04-2023
• Subjects: Biogeochemical Cycling; Chemical analysis; Chemiluminescence; Chromatography; Contamination; Conversion ratio; Detection limits; Environmental protection; Excimers; Ions; Irradiation; Luminescence; Luminol - chemistry; Nitrates; Nitrates - analysis; Nitrites - analysis; Nitrogen cycle; Nitrogen Dioxide; Peroxynitrite; Peroxynitrous Acid - chemistry; Photochemicals; Public health; Seawater; Water analysis; photoconversion; excimer lamp; nitrite; peroxynitrite; seawater; chemiluminescence; nitrate; luminol
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/acs.est.3c00273

Sensitive detection methods for nitrite (NO2 –) and nitrate (NO3 –) 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 NO2 – and NO3 –, 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 NO2 – and NO3 – 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 NO2 – and NO3 – 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 NO2 – and NO3 – detection in various samples.