Complexometric Titration

Complexometric titration is defined as a form of volumetric analysis in which the formation of a coloured complex is used to indicate the endpoint of the titration (1). Complexometric titrations rely on the formation of complexes between metal ions and compounds capable of donating electrons to form a stable, soluble complex (2). The complex is formed as a result of metal ions being titrated with a complexing agent or ligand. The principle of complexometric titrations is based on a simple ion being transformed into a complete ion and using a metal indicator to determine the endpoint (3), and the displacement of water from the solvation sphere of the metal ions by ligands (5). Different indicators are used in complexometric titrations as they have different pH ranges as well as detecting different metals in those ranges (1). Therefore complexometric titrations are useful in determining a mixture of different metals (1).

There are 4 types of complexometric titrations, namely direct titration, back titration, replacement titration and indirect titration (3). Direct titration is similar to an acid-base titration, whereby a standard chelon solution is added to the metal ion until the endpoint is detected (3). Although this method is the most convenient, it is limited by slow complexation reaction and interference due to the presence of other ions (3). In back titration an excess of standard EDTA solution is added to the metal solution to be analysed and the excess is back titrated to with a standard solution of a second metal ion (3). In replacement titration, the metal to be analysed displaces quantitatively from the complex (3). When the first 2 methods do not give a sharp endpoint, the metal may be determined by the displacement ...

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...rated against a known volume of EDTA

References

www.srmuniv.ac.in/downloads/Complexometric_Titration.pdf

Cairns, D. (2008). Essentials of Pharmaceutical Chemistry. Third Edition. Pharmaceutical Press. London. Great Britain. p152 – 154

Husain, A. (2007). Pharmaceutical Analysis: Theoretical Basis of Analysis. Complexometric Titrations. Department of Pharmaceutical Chemistry, Faculty of Pharmacy. Jamia Hamdard. Hamdard Nagar New Delhi. India

www.pharma-board.com/fop-drs/drawady/3rd_partII.pdf

Tandlich, R. (2014). Pharmaceutical Chemistry. Complexometric Titrations. Rhodes University. Grahamstown. South Africa. Slide 59-82

www.bionmr.un/edu/courses/chem221/lectures/chapter-12.ppt

Chemlab.truman.edu/CHEM222manual/pdf/edta.pdf

Furia, T. E. (1980). CRC Handbook of Food Additives, Second Edition, Volume 2. CRC Press. Florida. United States of America. p274