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The Quantitative Assay of Minerals for Fe 2+ and Fe 3+ Using 1,10‐Phenanthroline: II. A Photochemical Method
Author(s) -
Stucki J. W.
Publication year - 1981
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1981.03615995004500030040x
Subject(s) - chemistry , phenanthroline , ferric , detection limit , calibration curve , ferric iron , mineral , analytical chemistry (journal) , digestate , fluorescence , inorganic chemistry , nuclear chemistry , ferrous , environmental chemistry , chromatography , anaerobic digestion , physics , organic chemistry , quantum mechanics , methane
Abstract A photochemical method for measuring Fe 3+ and total Fe in minerals is described. The method determines Fe 2+ concentration by measuring the Fe(phen) 3 2+ (phen = 1,10‐phenanthroline) complex formed during HF‐H 2 SO 4 digestion of the mineral. To measure Fe 2+ accurately in the presence of Fe 3+ from the mineral, the sample digestion and analysis are performed under red light to prevent photochemical reduction of the ferric‐phen species. Total iron is measured by converting any Fe 3+ in the digestate to Fe(phen) 3 2+ by photochemical reduction using a fluorescent lamp. This procedure avoids the problems associated with adding chemical reducing agents to iron‐phen solutions. The calibration curves were linear up to 8‐µg Fe/ml with a lower detection limit of 0.011 µg/ml. The absorptivities of the calibration curves were 0.1852 ± 0.0017 and 0.1960 ± 0.0018 ml/cm‐µg for Fe 2+ and total Fe, respectively. Ferric iron in the mineral samples was calculated by difference.