Enhancing the possibilities of 57Fe Mössbauer spectrometry to the study of chemical and physical properties of iron in medicines

Abstract

57Fe Mössbauer spectrometry (MS) has long been used to study medicines that contain organic and inorganic iron-based compounds. The technique contributes to identify the type of iron compound, to reveal the presence of impurities, and to determine the coordination polyhedron, valence and spin states of iron in these materials. The possibilities of MS can be additionally enhanced if the recoilless f-fraction of the iron compound in the medicine is determined. In this work, we apply the full capabilities of MS to investigate the properties of iron in six commercial medicines. From the hyperfine parameters, we identify ferrous sulfate and ferrous fumarate as the iron compounds composing those samples. The iron ions are in high spin divalent oxidation states in octahedral coordination. The quadrupole splitting values for heptahydrated and anhydrous ferrous sulfates are found to be very similar in two medicines. Some medicines were found to be contaminated with ferric compounds. We reported the relative recoilless f-fractions of the ferrous compounds in these samples and from these data we determine the unknown amount of ferrous content in one medicine. This value was estimated at about 47% or 77% per tablet, assuming anhydrous or heptahydrated ferrous sulfate, respectively, in fair agreement with those obtained from a chemical method.