64378 2025 eng 2692 2701 10 40 article Royal Society of Chemistry (RSC) 1 -- -- -- Accurate nitrate and nitrite data support water-quality regulation, yet routine methods rely on external calibration and rarely achieve SI traceability. We report a calibration-free determination of nitrate and nitrite by combining isotope dilution with high-resolution continuum-source graphite furnace molecular absorption spectrometry (ID-HR-CS-GF-MAS). A 15N-enriched nitrate spike (its concentration verified by reverse isotope dilution against the standard reference material NIST 3185) provides the SI link, and it is gravimetrically added to samples; nitrate and residual nitrite are converted in situ to nitric oxide (NO), whose 215 nm band is recorded at a pixel resolution of λ/Δλ ≈ 140 000. The 0.2127 nm shift between 14NO and 15NO electronic spectra is resolved, and a three-latent-variable partial least squares regression model yields the 15N/14N ratio with 0.3% precision. Instrumental LoD values of 4.8 ng (14N) and 3.2 ng (15N) translate to a method LoD of 4.8 ng of nitrogen (equivalent to 1.05 mg L−1 NO3− for a 20 μL aliquot). The furnace program allows for successive drying/pyrolysis loops, so additional 20 μL aliquots can be layered onto the graphite platform. Alternatively, a 10 mL anion-exchange solid-phase extraction step concentrates nitrate and nitrite fivefold, allowing for the analysis of even lower sample concentrations. Results for four certified reference materials (2.9 to 1000 mg L−1 NO3−) agreed with certified values, giving relative expanded uncertainties of 2 to 4%. Analysis of twenty Berlin surface-water samples revealed concentrations ranging from 0.10 to 7.3 mg L−1 NO3−, indicating that the Panke River and Teltow Canal are the primary sources of nitrogen. ID-HR-CS-GF-MAS thus delivers ID-MS-level accuracy in a few minutes per run with bench-top optics, and, with optional on-platform or SPE pre-concentration, extends SI-traceable nitrate/nitrite monitoring into the low-ng regime. Journal of Analytical Atomic Spectrometry 0267-9477 10.1039/D5JA00252D urn:nbn:de:kobv:b43-643785 true journal-article http://creativecommons.org/licenses/by/3.0/ crossref PersonAuthorFirstName_1,PersonAuthorLastName_1,PersonAuthorIdentifierOrcid_1,PersonAuthorFirstName_2,PersonAuthorLastName_2,PersonAuthorFirstName_3,PersonAuthorLastName_3,PersonAuthorFirstName_4,PersonAuthorLastName_4,PersonAuthorIdentifierOrcid_4,PublisherName,TitleMain_1,Language,TitleAbstract_1,TitleParent_1,PageFirst,PageLast,Issue,Volume,PublishedYear,IdentifierIssn,Enrichmentlocal_crossrefLicence doi-import 16.10.2025 false true Creative Commons - CC BY - Namensnennung 4.0 International Carlos Enrique Abad Andrade Dennis Jegielka Allen Aloysius Sebastian Recknagel eng uncontrolled Isotope dilution eng uncontrolled Nitrate and nitrite determination eng uncontrolled SI-traceable quantification eng uncontrolled Calibration-free analysis eng uncontrolled Water quality eng uncontrolled Berlin surface waters eng uncontrolled NO molecular absorption bands Analytische Chemie Sanitär- und Kommunaltechnik; Umwelttechnik 1 Analytische Chemie; Referenzmaterialien 1.6 Anorganische Referenzmaterialien und Gasanalytik Umwelt Umwelt-Material-Interaktionen Chemie und Prozesstechnik Chemische Charakterisierung und Spurenanalytik Verlagsliteratur Datei für die Öffentlichkeit verfügbar ("Open Access") Wissenschaftliche Artikel der BAM Bundesanstalt für Materialforschung und -prüfung (BAM) https://opus4.kobv.de/opus4-bam/files/64378/Abad_et_al_d5ja00252d.pdf https://opus4.kobv.de/opus4-bam/files/64378/Support_information_Abad_et_al_d5ja00252d.pdf