There are many types of chemical methods to determine or check the concentration of a solution, one of which is complexometric titration. In this review, you will be introduced to this method which is also known as chelatometry. It is so called because of the formation of a compound or chelate complex that will occur during the titration process.
You can find out more about this type of titration that has been developed since the last few decades from the reviews below.
What is Complexometric Titration
As mentioned earlier, this complexometric titration is a type of titration that refers to the process of complexation reactions, including the formation of complex ions. In the process, titrant and titrate will react with each other. At the end of the process an experience usually consists of two components in the form of a ligand.
Ligands are simple molecules. Especially in complex compounds, ligands function to donate electron pairs. This one titration method is generally used to analyze the concentration of metal compounds
Complexometric Titration Indicator
Like other titration methods, complexometry also has its own indicator for measuring the content of a substance. This indicator in the titration process will also show a color change. The color change occurs depending on the specific type of metal ion or the type of metal ion being tested.
Indicators in the complexometric method are also known as PM indicators or metallochromic indicators. This indicator is basically a water-soluble organic molecule. Some examples of compounds that can be used as complexometric indicators include calcein, hematoxylin, eriochrome, and curcumin.
Basic Principles of Complexometry
Next what you need to know is the basic principle of this complexometric titration method. Complexometry works when there is the formation of complex ions between the compound being used as an indicator and the compound to be measured. When the titration process is complete, the indicator will change color to clear.
Complexometry measures the content of a substance by calculating the volume of the solution, either the titrant solution or the indicator itself or the solution being measured. This method is quite commonly practiced in the medical and pharmaceutical fields because the measurement results are considered specific and have a fairly high accuracy.
How Complexometry Works
The sensitivity and convenience offered by the complexometric titration method can be the main reasons why this method is still used frequently. In fact, for metal titration, there are also several other methods that can be used. For complexometry itself, there are often two more derivative ways that can be used, namely the Schwarzenbach method and the Liebig method.
Let's start from the Schwarzenbach way. Schwarzenbach's titration method uses a polydentate ligand. A polydentate ligand is a simple molecule in which there are more than two donor atoms. This donor atom will be used to bind the metal or central ion. The polidentate ligands used are mainly polycarboxylic amine acids such as EDTA (Ethylenediaminetetraacetic Acid).
This EDTA is a four base organic acid. The Schwarzenbach method is usually used to measure the concentration of metal or calcium in the sample being tested. Calcium or metal is what will experience the complex from EDTA. The aforementioned color of the metallochromic indicator will show an indication of its content.
A little additional information too, Schwarzenbach is the one who discovered the visual color indicator in this complexometric method. Schwarzenbach discovered it in the 1940's, a sensitive indicator of the level of metal ions present in the sample solution. This indicator is also known as a complexometric indicator.
Next is the Liebig method. Whereas the Schwarzenbach method uses polydentate ligands, the Liebig method uses monodentate ligands, which are simple molecules that only have a single donor atom. In this method, silver nitrate (AgNO3) acts as a titrant. This method is generally used to determine the level of cyanide in a sample.
That's a brief discussion about complexometry. One thing that makes this method feel not too different from other titration methods is probably the titration tool used. What distinguishes complexometric titration from other methods is the indicator described above.