{"title":"A new 1,10-phenanthroline method for oxalate-extractable iron measurement","authors":"Yan Zhang , Yi Liu","doi":"10.1016/j.apgeochem.2025.106354","DOIUrl":null,"url":null,"abstract":"<div><div>Iron separation from different solid phases is essential for evaluating the environmental function of iron in sediments. Oxalate is a commonly used extractant that effectively extract iron(hydro)oxides in sediments by complexation. However, when using spectrophotometry method, excess oxalate will interfere the complexation of iron with 1,10-phenanthroline leading to the failure of iron measurement. In this study, we discovered an effective method for spectrophotometric analysis of iron samples with oxalate by adjusting the pH to 7–9, which changes the structure of the Fe-oxalate complexes and ensured the complexation of iron with 1,10-phenanthroline. Further exploration indicates that photolysis and heating also decompose Fe-oxalate complexes, but the performance is not as good as pH adjustment. The standard solution exhibits a strong linear relationship between absorbance (<em>Abs</em>) and concentration (<em>Con</em>): <em>Abs</em> = 0.1934 × <em>Con</em> + 0.1360, with a R<sup>2</sup> of 0.9997, accuracy of 97.1 %, and relative standard deviation of 1.4 %, which demonstrate the reliability of this method. Overall, the pretreatment is simple, and the influence of the organic solvent (oxalate) is diminished after pH adjustment. This method is expected to contribute to community by providing a new reliable, effective, less pre-treatment, economical, and sensitive testing approach and hopefully assist in the investigation on environmental function of iron minerals.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"183 ","pages":"Article 106354"},"PeriodicalIF":3.1000,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Applied Geochemistry","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0883292725000770","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
Iron separation from different solid phases is essential for evaluating the environmental function of iron in sediments. Oxalate is a commonly used extractant that effectively extract iron(hydro)oxides in sediments by complexation. However, when using spectrophotometry method, excess oxalate will interfere the complexation of iron with 1,10-phenanthroline leading to the failure of iron measurement. In this study, we discovered an effective method for spectrophotometric analysis of iron samples with oxalate by adjusting the pH to 7–9, which changes the structure of the Fe-oxalate complexes and ensured the complexation of iron with 1,10-phenanthroline. Further exploration indicates that photolysis and heating also decompose Fe-oxalate complexes, but the performance is not as good as pH adjustment. The standard solution exhibits a strong linear relationship between absorbance (Abs) and concentration (Con): Abs = 0.1934 × Con + 0.1360, with a R2 of 0.9997, accuracy of 97.1 %, and relative standard deviation of 1.4 %, which demonstrate the reliability of this method. Overall, the pretreatment is simple, and the influence of the organic solvent (oxalate) is diminished after pH adjustment. This method is expected to contribute to community by providing a new reliable, effective, less pre-treatment, economical, and sensitive testing approach and hopefully assist in the investigation on environmental function of iron minerals.
期刊介绍：
Applied Geochemistry is an international journal devoted to publication of original research papers, rapid research communications and selected review papers in geochemistry and urban geochemistry which have some practical application to an aspect of human endeavour, such as the preservation of the environment, health, waste disposal and the search for resources. Papers on applications of inorganic, organic and isotope geochemistry and geochemical processes are therefore welcome provided they meet the main criterion. Spatial and temporal monitoring case studies are only of interest to our international readership if they present new ideas of broad application.
Topics covered include: (1) Environmental geochemistry (including natural and anthropogenic aspects, and protection and remediation strategies); (2) Hydrogeochemistry (surface and groundwater); (3) Medical (urban) geochemistry; (4) The search for energy resources (in particular unconventional oil and gas or emerging metal resources); (5) Energy exploitation (in particular geothermal energy and CCS); (6) Upgrading of energy and mineral resources where there is a direct geochemical application; and (7) Waste disposal, including nuclear waste disposal.
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