Separation and indirect ultraviolet detection of ferrous and trivalent iron ions by using ionic liquids in ion chromatography

A method of simultaneous separation and indirect ultraviolet detection of different valence iron ions Fe2+ and Fe3+ by using ionic liquids as mobile phase additives and ultraviolet absorption reagents on a cation exchange column functionalized with carboxylic acid groupwas developed. The effects of ionic liquids, organic acids, detection wavelength, etc. on separation and detection of Fe2+ and Fe3+ were investigated and the mechanism was discussed. The pyridinium and imidazolium ionic liquids were not only ultraviolet absorption reagents of indirect ultraviolet detection but also effective components for separating Fe2+ and Fe3+. The separation and detection of Fe2+ and Fe3+ can be achieved using 0.5 mmol/L pyridinium ionic liquid-1.2 mmol/L methanesulfonic acid as the mobile phase. The determination of Fe2+ and Fe3+ had a good linear relationship in the concentration range of 1-100 mg/L. The limits of detection of Fe2+ and Fe3+ were 0.12 and 0.09 mg/L, respectively. This method was applied to the actual sample detection in the field of medical analysis. The spiked recoveries were between 97.3 and 99.5%, and the relative standard deviations were less than 0.6%. The method is simple, accurate, and reliable, and is an analytical method with universal and practical value.