A range of hydroperoxides were reduced by ferrous ions in acid solutions and the amount of ferric product was measured as a xylenol orange complex at 560 nm. Dilute sulfuric acid, 50% acetic acid, and acidified 90% methanol proved to be suitable solvents. The color developed within 15 min and was st
Determination of Iron in Solutions with the Ferric–Xylenol Orange Complex
✍ Scribed by Craig Gay; James Collins; Janusz M. Gebicki
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 78 KB
- Volume
- 273
- Category
- Article
- ISSN
- 0003-2697
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✦ Synopsis
Formation of a colored complex between ferric iron and xylenol orange has been used in a variety of applications, but there is disagreement about the number of complexes that exist, their stoichiometry, pH dependence, solvent effects, and other parameters. In this study we investigated the use of the complex to measure micromolar concentrations of iron in aqueous and alcohol solutions. The results show that the optimum wavelength for the measurement is 560 nm, that only a 1:1 ferric:xylenol orange complex forms, and that its molar absorption coefficient is affected by the solvent, the source of the xylenol orange, and the pH. Under the recommended conditions, formation of the complex is completed in less than 5 min and it is stable in several solvents. Its molar absorption coefficient in 25 mM H 2 SO 4 is 20,100 or 14,500 M ؊1 cm ؊1 , depending on the source of the dye. A recommended protocol for the use of the assay is given.
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It niny not bo gcncrrrlly known tlint ferric iron niny bo w r y rapidly cstiinntctl witli fnir nccurncy by on iodoniotrio rnotliotl (which docv not inrolro rciliic:tion) without tnking nny spccinl precnutio~is. To obtnin tho best rcsiilts, i t is doubtless ncccssnry to follow the inctliod of JIoiir
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