Water triggered structural transitions in Fe-gluconate

Fe-gluconate, Fe(C6H11O7)(2)center dot xH(2)O is a well-known material widely used for iron supplementation, in the food industry as a coloring agent, in cosmetic industry for skin and nail conditioning, and metallurgy. Despite of a wide range of applications, its physical properties were not studied extensively. In this study, Fe-gluconate with three different amounts of water viz. x = 2 (fully hydrated), 0 < x < 2 (intermediate), and x = 0 (dry) were investigated by means of X-ray diffraction (XRD) and Mossbauer spectroscopic (MS) methods. The former in the temperature range of 20-425 K, and the latter at 295 K. Based on the XRD measurements, crystallographic structures were determined: monoclinic (space group I2) for the hydrated sample and triclinic (space group P1) for the dry sample. The partially hydrated sample was two-phased. Unit cell parameters for both structures show strong, very complex and non-monotonic temperature dependences. Mossbauer spectroscopic measurements gave evidence that iron in all samples exists in the form of Fe(II) and Fe(III) ions. The amount of the latter equals to similar to 30% in the hydrated sample and to similar to 20% in the dry one.

Automated summary

The study investigated iron gluconate with different water content using X-ray diffraction and Mossbauer spectroscopy, revealing a correlation between crystal structure and water content, with complex temperature-dependent variations in unit cell parameters for different structures. Iron in all samples exists in the form of Fe(II) and Fe(III) ions, with varying percentages depending on the hydration level.