Characterization and Thermal Behavior of the Iron Dietary Supplement Ferrous Glycine Sulfate Pentahydrate

Abstract

Ferrous glycine sulfate pentahydrate [Fe(glycine)(SO4)·5H2O with glycine = C2H5NO2], contained in the supplement for treating iron deficiency anaemia, commercially known as ferro sanol duodenal®, was characterized by laboratory X‐ray powder diffraction (XRPD), scanning electron microscope (SEM), and infrared spectroscopy (IR). The thermal behavior was investigated by thermal analysis (TGA and DTA) and temperature‐dependent in situ XRPD measurements. Furthermore, the phase transitions to a less hydrated form [Fe(glycine)(SO4)·3H2O] and successively to the anhydrous form were demonstrated to occur in the crystalline solid state. Compared to the crystal structure of the pentahydrate, the trihydrate exhibits a different coordination environment of the iron sites where glycine ligands bridge iron forming a 1D polymeric chain structure. From detailed structural comparison, the mechanism of the phase transitions can be concluded.