This application note illustrates a method for accurately determining the concentration of Fe2+ and Fe3+ metal ions within the same sample solution using complexometric titration with EDTA and photometric detection with a DP5 Phototrode™. This method gives accurate results even in the presence of other metal ions.
What Is the Importance of Accurately Measuring Fe2+ and Fe3+ Metal Ions?
Accurate measurement of Fe2+ and Fe3+ metal ions is important in various applications, such as biological systems, industrial processes, and research. It can provide insight into the total iron content and the individual amounts of each oxidation state present in a sample.
How Does Complexometric Titration with EDTA Work to Measure Fe2+ and Fe3+?
At low pH, the EDTA complex formed with Fe3+ is more stable than with Fe2+, making Fe3+ ions titrated preferentially. After total Fe3+ is titrated, the remaining Fe2+ is oxidized to Fe3+ and determined using EDTA as a titrant. The titration is monitored photometrically using salicylic acid or 5-sulfosalicylic acid as a color indicator.
What Metal Ions Can Interfere with Photometric Detection in This Method?
Co2+, Cu2+, and Ni2+ metal ions can interfere with photometric detection since they generate intensely colored solutions that overlap with the peak of the Fe3+-indicator complex. To avoid this, one can measure at 620 nm or adjust the endpoint accordingly.
This Application Note Includes
- An introduction to the method
- Sample preparation and procedures
- Solutions and chemicals
- Chemistry
- Instruments and accessories
- Results and remarks
Method files (.lmt and .xml) are also included for direct import and implementation of the instrument.
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