{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,16]],"date-time":"2026-02-16T20:55:40Z","timestamp":1771275340131,"version":"3.50.1"},"reference-count":61,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2024,6,27]],"date-time":"2024-06-27T00:00:00Z","timestamp":1719446400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003593","name":"Brazilian agency CNPq","doi-asserted-by":"publisher","award":["305479\/2021-0"],"award-info":[{"award-number":["305479\/2021-0"]}],"id":[{"id":"10.13039\/501100003593","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100003593","name":"Brazilian agency CNPq","doi-asserted-by":"publisher","award":["001"],"award-info":[{"award-number":["001"]}],"id":[{"id":"10.13039\/501100003593","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002322","name":"Coordination for the Improvement of Higher Education Personnel\u2014Brazil (CAPES)","doi-asserted-by":"publisher","award":["305479\/2021-0"],"award-info":[{"award-number":["305479\/2021-0"]}],"id":[{"id":"10.13039\/501100002322","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002322","name":"Coordination for the Improvement of Higher Education Personnel\u2014Brazil (CAPES)","doi-asserted-by":"publisher","award":["001"],"award-info":[{"award-number":["001"]}],"id":[{"id":"10.13039\/501100002322","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>The concept of uncertainty in an isotopic analysis is not uniform in the scientific community worldwide and can compromise the risk of false compliance assessment applied to carbon isotopic analyses in natural gas exploratory evaluation. In this work, we demonstrated a way to calculate one of the main sources of this uncertainty, which is underestimated in most studies focusing on gas analysis: the \u03b413C calculation itself is primarily based on the raw analytical data. The carbon isotopic composition of methane, ethane, propane, and CO2 was measured. After a detailed mathematical treatment, the corresponding expanded uncertainties for each analyte were calculated. Next, for the systematic isotopic characterization of the two gas standards, we calculated the standard uncertainty, intermediary precision, combined standard uncertainty, and finally, the expanded uncertainty for methane, ethane, propane, and CO2. We have found an expanded uncertainty value of 1.8\u2030 for all compounds, except for propane, where a value of 1.6\u2030 was obtained. The expanded uncertainty values calculated with the approach shown in this study reveal that the error arising from the application of delta calculation algorithms cannot be neglected, and the obtained values are higher than 0.5\u2030, usually considered as the accepted uncertainty associated with the GC-IRMS analyses. Finally, based on the use of uncertainty information to evaluate the risk of false compliance, the lower and upper acceptance limits for the carbon isotopic analysis of methane in natural gas are calculated, considering the exploratory limits between \u221255\u2030 and \u221250\u2030: (i) for the underestimated current uncertainty of 0.5\u2030, the lower and upper acceptance limits, respectively, are \u221254.6\u2030 and \u221250.4\u2030; and (ii) for the proposed realistic uncertainty of 1.8\u2030, the lower and upper acceptance limits would be more restrictive; i.e., \u221253.5\u2030 and \u221251.5\u2030, respectively.<\/jats:p>","DOI":"10.3390\/molecules29133065","type":"journal-article","created":{"date-parts":[[2024,6,27]],"date-time":"2024-06-27T08:57:50Z","timestamp":1719478670000},"page":"3065","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Measurement Uncertainty and Risk of False Compliance Assessment Applied to Carbon Isotopic Analyses in Natural Gas Exploratory Evaluation"],"prefix":"10.3390","volume":"29","author":[{"given":"Fabiano","family":"Leal","sequence":"first","affiliation":[{"name":"Research Center, Petrobras S.A., Rio de Janeiro 21941-915, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alexandre","family":"de Andrade Ferreira","sequence":"additional","affiliation":[{"name":"Research Center, Petrobras S.A., Rio de Janeiro 21941-915, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7247-9888","authenticated-orcid":false,"given":"Gabriel","family":"Silva","sequence":"additional","affiliation":[{"name":"Center for Energy Resources Engineering, Department of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kongens Lyngby, Denmark"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tulio","family":"Freire","sequence":"additional","affiliation":[{"name":"Research Center, Petrobras S.A., Rio de Janeiro 21941-915, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Marcelo","family":"Costa","sequence":"additional","affiliation":[{"name":"Research Center, Petrobras S.A., Rio de Janeiro 21941-915, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Erica","family":"de Morais","sequence":"additional","affiliation":[{"name":"Research Center, Petrobras S.A., Rio de Janeiro 21941-915, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jarbas","family":"Guzzo","sequence":"additional","affiliation":[{"name":"Research Center, Petrobras S.A., Rio de Janeiro 21941-915, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8979-4131","authenticated-orcid":false,"given":"Elcio","family":"de Oliveira","sequence":"additional","affiliation":[{"name":"Postgraduate Programme in Metrology, Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro 22451-900, Brazil"},{"name":"Land Transportation and Storage, Measurement and Product Inventory Management, Logistics, Petrobras S.A., Rio de Janeiro 20231-030, Brazil"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2024,6,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Souza, M.A., Gonz\u00e1lez, M.O.A., and Pinho, A.L.S.d. 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