{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,23]],"date-time":"2026-07-23T03:11:51Z","timestamp":1784776311609,"version":"3.55.0"},"reference-count":11,"publisher":"Wiley","issue":"3","license":[{"start":{"date-parts":[[2024,11,26]],"date-time":"2024-11-26T00:00:00Z","timestamp":1732579200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["278676953"],"award-info":[{"award-number":["278676953"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["317438550"],"award-info":[{"award-number":["317438550"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001659","name":"Deutsche Forschungsgemeinschaft","doi-asserted-by":"publisher","award":["426547801"],"award-info":[{"award-number":["426547801"]}],"id":[{"id":"10.13039\/501100001659","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["analyticalsciencejournals.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Rapid Comm Mass Spectrometry"],"published-print":{"date-parts":[[2025,2,15]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Rationale<\/jats:title>\n                    <jats:p>The analysis of nitrogen isotopes in aqueous dissolved nitrate is an effective method for identifying pollution sources and offers the potential to study the nitrogen cycle. However, the measurement of nitrogen isotope ratios of nitrate still requires extensive sample preparation or derivatization.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      In this study, a modified commercially available liquid chromatography\u2013isotope ratio mass spectrometer (LC\u2010IRMS) interface is presented that enables automated measurement of\n                      <jats:italic>\u03b4<\/jats:italic>\n                      <jats:sup>15<\/jats:sup>\n                      N signatures from nitrate by online reduction of nitrate in two consecutive steps. First, vanadium(III) chloride is used as a reducing agent to convert NO\n                      <jats:sub>3<\/jats:sub>\n                      <jats:sup>\u2212<\/jats:sup>\n                      to N\n                      <jats:sub>\n                        <jats:italic>x<\/jats:italic>\n                      <\/jats:sub>\n                      O\n                      <jats:sub>y<\/jats:sub>\n                      under acidic conditions. The mix of nitrogen oxides is then transferred into a stream of helium and reduced to nitrogen (N\n                      <jats:sub>2<\/jats:sub>\n                      ) analysis gas via a hot copper reactor. Prior to the online conversion of aqueous nitrate into elemental nitrogen, the sample was chromatographically separated from potential matrix effects on a PGC column.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Precision was achieved at a level below 1.4\u2030 by injecting 10\u2009\u03bcL of 50\u2009mg\u2009L\n                      <jats:sup>\u22121<\/jats:sup>\n                      N, using five different nitrate standards and reference materials. These materials spanned a range of more than 180\u2030 in\n                      <jats:italic>\u03b4<\/jats:italic>\n                      <jats:sup>15<\/jats:sup>\n                      N. To demonstrate the applicability of the method, we measured water samples from an enrichment experiment, where isotopically enriched ammonium chloride was administered into a small river over the course of 2\u2009weeks. In contrary to our expectation, the \u03b4\n                      <jats:sup>15<\/jats:sup>\n                      N values of river nitrate showed values between +0.4\u2009\u00b1\u20090.4\u2030 and +4.1\u2009\u00b1\u20090.3\u2030, varying over a small range of 3.7\u2030.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Our study showed that the measurement of nitrate nitrogen isotope ratios with a modified LC\u2010IRMS system is possible but that further modifications and improvements would be necessary for a robust and user\u2010friendly instrument.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/rcm.9950","type":"journal-article","created":{"date-parts":[[2024,11,26]],"date-time":"2024-11-26T07:34:56Z","timestamp":1732606496000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["A Proof\u2010of\u2010Principle Study for\n                    <i>\u03b4<\/i>\n                    <sup>15<\/sup>\n                    N Measurements of Aqueous Dissolved Nitrate With a Modified LC\u2010IRMS Interface"],"prefix":"10.1002","volume":"39","author":[{"given":"Tobias","family":"Hesse","sequence":"first","affiliation":[{"name":"Instrumental Analytical Chemistry University of Duisburg\u2010Essen  Essen Germany"},{"name":"Probenahmedienst Feststoffe, Ressourcen\u2010 und Qualit\u00e4tsmanagement Landesamt f\u00fcr Natur, Umwelt und Verbraucherschutz NRW  Duisburg Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Felix","family":"Niemann","sequence":"additional","affiliation":[{"name":"Instrumental Analytical Chemistry University of Duisburg\u2010Essen  Essen Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shaista","family":"Khaliq","sequence":"additional","affiliation":[{"name":"Instrumental Analytical Chemistry University of Duisburg\u2010Essen  Essen Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Daniel","family":"K\u00f6ster","sequence":"additional","affiliation":[{"name":"Institut f\u00fcr Arbeitsschutz der DGUV (IFA) Deutsche Gesetzliche Unfallversicherung e.V. (DGUV)  Sankt Augustin Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Julian","family":"Enss","sequence":"additional","affiliation":[{"name":"Aquatic Ecology, Faculty of Biology University of Duisburg\u2010Essen  Essen Germany"},{"name":"Centre for Water and Environmental Research University of Duisburg\u2010Essen  Essen Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Christian\u00a0K.","family":"Feld","sequence":"additional","affiliation":[{"name":"Aquatic Ecology, Faculty of Biology University of Duisburg\u2010Essen  Essen Germany"},{"name":"Centre for Water and Environmental Research University of Duisburg\u2010Essen  Essen Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Milen","family":"Nachev","sequence":"additional","affiliation":[{"name":"Aquatic Ecology, Faculty of Biology University of Duisburg\u2010Essen  Essen Germany"},{"name":"Centre for Water and Environmental Research University of Duisburg\u2010Essen  Essen Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Klaus","family":"Kerpen","sequence":"additional","affiliation":[{"name":"Instrumental Analytical Chemistry University of Duisburg\u2010Essen  Essen Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maik\u00a0A.","family":"Jochmann","sequence":"additional","affiliation":[{"name":"Instrumental Analytical Chemistry University of Duisburg\u2010Essen  Essen Germany"},{"name":"Centre for Water and Environmental Research University of Duisburg\u2010Essen  Essen Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Torsten\u00a0C.","family":"Schmidt","sequence":"additional","affiliation":[{"name":"Instrumental Analytical Chemistry University of Duisburg\u2010Essen  Essen Germany"},{"name":"Centre for Water and Environmental Research University of Duisburg\u2010Essen  Essen 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