Factors affecting non aqueous titration

Non-aqueous titration is the titration of analytes that are weakly acidic or basic in the absence of water. A non-aqueous solvent is used to dissolve the solute, which is then titrated with an acid or base titrant.

Both acid-base titration and non-aqueous titration work on the same basic principle (Brønsted-Lowry Theory). According to this, a base donates a proton to another chemical, and a base accepts a proton.

The interference of water molecules in the titration is the rationale for non-aqueous titrations. Water is both a weak acid and a basic. When different bases and acids are dissolved in water, the water molecules compete with each other for proton donation and acceptance. Accordingly, a titration method that does not involve the interference of water molecules is necessary; as a result, non-aqueous solvents are used in a procedure known as non-aqueous titration to assess compounds.

In a non-aqueous titration, there are four types of solvents that are used. These are aprotic solvents, protogenic solvents, protophilic solvents, and amphiprotic solvents. Some examples of non-aqueous solvents are glacial acetic acid, ether, acetonitrile, nitrogen tetroxide, alcohols, carbon disulphide, benzene, chloroform, acetone, formic acid, ammonia, etc.

Crystal violet indicator, methyl red indicator, naphtholbenzein indicator, quinaldine red, thymol blue, etc. are used as indicators for non-aqueous titrations to detect the endpoint/equivalence point of the titration. Depending on the nature of the titrant, each indicator has a distinct color change at the end of the reaction.

Factors that affect non-aqueous titration:

• Temperature: The volume of non-aqueous solutions used is affected by temperature, which causes the concentration of the sample to fluctuate. Temperature affects non-aqueous solvents because they expand more than water.
• Highly acidic or basic condition: In the process of titrating weak bases or acids, the addition of very acidic or basic solvents raises the level of acidity or basicity, which increases the consumption of titrant.
• Moisture level: When doing non-aqueous titrations, it is important to stay away from moisture in order to neutralize the solution and make the endpoint more accurate.
• Acid-base characteristics of the solvents used: In a non-aqueous titration, the end-point is affected by the acid-base characteristics of the solvents used.
• Protolysis of the substance: The endpoint of the reaction may increase due to the protolysis of the substance.
• Dielectric constant: Solvents with low dielectric constants are often used in non-aqueous titrations, which produce sharp endpoints.
• Carbon dioxide: The endpoint of acid-base titrations can be affected when carbon dioxide (CO2) from the air dissolves in water and forms carbonic acid, so it should be controlled.