Spectrophotometric study of iron oxidation in the iron(II)/azide/tetrahydrofuran system and some analytical applications Original Research Article

A simple, sensitive and alternative method for the spectrophotometric determination of iron(II or III) has been established. The procedure is based on the formation of iron-III/azide complexes, in 70% (v/v) tetrahydrofuran (THF)/water medium. Under these present experimental conditions, ferrous iron is rapidly oxidized and complexed. The high sensitivity obtained in this method is due to the use of an interesting absorption band caused by THF solvation. In the recommended conditions, absorbances for the ferric complexes are measured at 396 nm, where the molar absorptivity is 1.53×104 l mol−1 cm−1. The organic solvent utilized increases the sensitivity and the stability of the measurements. The reproducibility is shown by an average deviation about 0.15%. This system obeys the Beer’s law and is suitable for iron determination in the concentration range from 0.6 to 2.8 ppm (15–65% T, quartz cells of 1.00 cm). The optimal conditions for a faster iron-II oxidation were determined by studying the different factors involved. The influence of various diverse ions was also evaluated. Analytical applications have been tested for several different materials (iron-rocks), including pharmaceutical products for anemia, in which the results were compared with atomic absorption measurements. Very good concordances were obtained between these two different techniques, showing the potential of present spectrophotometric method in iron analysis.