Production of hydroxyl radicals by iron solid compounds†

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Abstract
The deleterious effects of radicals in biological systems are now admitted. The aim of the present work was to study the reduction of oxygen and hydrogen peroxide (H2O2) into hydroxyl radicals by selected iron compounds in a phosphate buffered solution. Radical detection has been carried out by electron spin resonance spectroscopy (ESR) with “spin trapping”; (5,5‐dimethyl‐1‐pyrroline N‐oxide, DMPO). The following minerals have been used: goethite (FeOOH a), akaganeite (FeOOH β), hematite Fe2O3α), magnetite (Fe3O4), siderite (FeCO3), and crocidolite fibres (Na2Fe3Si8O22(OH)2). Crocidolite and siderite reduced O2 into OH∗. Catalase inhibited this reduction. The reduction occurs at the mineral surface. When H2O2 was added to the buffer solution, goethite was inactive, akaganeite, magnetite, crocidolite and hematite were active and siderite was very active. These reactions could play a role in the mechanisms of toxic injury caused by some solid iron compounds.