Learn about the principle, types, and applications of non-aqueous titration, in which the analyte substance is dissolved in a solvent that does not contain water.
Titration is a specific quantitative chemical analysis used in laboratories to measure the concentration of a particular analyte.
Titration, also known as volumetric or titrimetry method, is a process in which titrant filled in burette (solution of known concentration) added to a conical flask (solution of unknown concentration) until the reaction is complete, and usually, an indicator is used to determine the endpoint of the reaction.
Acid-base, redox, precipitation, and complexometric titrations are different types of titrations. However, in the quantitative chemical analysis most commonly used are redox titrations and acid-base titrations.
What is non-aqueous titration?
Non-aqueous titration is a type of titration in which weakly acidic or basic analytes are carried out in a solvent medium that does not contain water. The solute is dissolved in a non-aqueous solvent and titrated with an acid or base titrant.
The principle of non-aqueous titration is the same as acid-base titration, which states that a substance that can donate a proton to another substance, is known as acid, and a substance that accepts a proton is called the base.
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The theory behind non-aqueous titrations:
Water can act as both a weak acid and a weak basic. Water competes efficiently in proton acceptance and proton donation when other weak acids or bases are dissolved in it.
However, titrating may not result in the correct endpoint. This is why non-aqueous titration is required. This approach is advantageous for accurate titration of weak acids and bases, as well as the ability of the non-aqueous solvent to dissolve organic molecules.
The Lowry-Bronsted theory's concepts may help to explain the different reactions that happen throughout many non-aqueous titrations. Therefore, an acid is a proton donor and a base is a proton acceptor.
Determination of the endpoint in non-aqueous titrations:
In non-aqueous titrations there are two methods are used to determine the endpoint: the potentiometric method and the indicator method.
Potentiometric method:
It is a method an endpoint is determined by using the reference electrode and indicator electrode. As a reference electrode, a saturated calomel electrode is used, and as an indicator electrode glass electrode is used.
Indicator method:
In this method, different indicators are used to detect the endpoint. They are employed in the sample solution before the reaction begins.
Indicators used in non-aqueous titration:
In a non-aqueous titration, visual indicators are most appropriate for detecting the endpoint or equivalence point of the reaction.
The indicators used in non-aqueous titrations are as follows:
For non-aqueous titration, the ionised and unionised form, or various resonant form of indicators are all generally applicable, however, the color change at the endpoint of reaction differ from titration to titration according to the nature of the titrant.
- Crystal violet indicator: It is the most commonly used titration indicator, used as a 0.5% w/v solution in glacial acetic acid.
- Methyl red indicator: It is prepared in a 0.2% w/v solution in dioxin and changes the color at the endpoint from yellow to red.
- Naphtholbenzein indicator: It is used as an indicator for acid-base titrations, prepared in 0.2% w/v solution in ethanoic acid, and shows the color changes at endpoint from yellow to green color.
- Quinaldine red: It is used for most drug assays, its color changes from purplish red to light green at the endpoint.
- Thymol blue: It is commonly used as a pH indicator in several types of titrations. It is used as a 0.2% w/v solution in methanol, its color changing from yellow to blue at the endpoint.
Types of non-aqueous titration solvents:
There are 4 types of solvents are used in non-aqueous titration are aprotic solvents, protophilic solvents, protogenic solvents, and amphiprotic solvents.
Aprotic solvents:
It is a type of non-aqueous solvent in which a hydrogen atom is bonded to oxygen, or fluorine, or nitrogen. These are neutral in charge and are chemically inert. Chloroform and benzene are two examples.
Protogenic solvents:
These types of solvents are acidic and readily donate protons. Generally, they are applied to increase the alkalinity of weak acids and strengthen weak bases. Acetic and acid sulphuric are two examples.
Protophilic solvents:
These types of solvents are basic solvents that have a high tendency to accept protons. When they react with acids, they form solvated protons. Amines liquid and ammonia are two examples.
Amphiprotic solvents:
These are solvents that have both acidic and basic properties, as well as the properties of protogenic and protophilic solvents. Acetic acid and alcohols are two examples.
Applications of non-aqueous titration:
Non-aqueous titrations have a wide range of applications in the different fields they are as follows.
- Pharmaceutical application is the major application of non-aqueous titration, as non-aqueous titration is very useful in the medicinal field.
- It is used to perform assays that allow us to determine the purity of compounds.
- It is used to control the purity of different types of chemicals.
- It is used in the determination of the composition of adrenergic and ant tubercular drugs.
- Non-aqueous titration is used to quantify the sample mixtures of primary, secondary, and tertiary amines.
- It is used to determine the hydrophobic compounds.
Commonly asked questions on non-aqueous titration are as follows.
Non-aqueous titration is based on which theory?
Non-aqueous titration is based on the Bronsted-Lowry principle.
Which compound titration is carried out by non-aqueous titration?
Non-aqueous titrations are those in which non-aqueous solvents are used to titrate weakly acidic or basic analytes to obtain a sharp endpoint.
Why non-aqueous titration is required?
Non-aqueous titration is important and required because water can act as both a weak acid and, a weak base and therefore can compete with other weak acids and bases dissolved in it in proton acceptance of proton donation.
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