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Chromatography - (Concept)
Chromatography is the technique for the separation, purification, and testing of compounds. In this process, we apply the mixture to be separated on a stationary phase (solid or liquid) and a pure solvent such as water or any gas is allowed to move slowly over the stationary phase, carrying the components separately as per their solubility in the pure solvent.
There are four main types of chromatography:
1. Adsorption chromatography
2. Column chromatography
3. Thin layer chromatography
4. Partition chromatography
Adsorption chromatography
In the process of adsorption chromatography, different compounds are adsorbed on the adsorbent to different degrees based on the absorptivity of the component. Here also, a mobile phase is made to move over a stationary phase, thus carrying the components with higher absorptivity to a lower distance than that with lower absorptivity.
Column chromatography
It is the technique used to separate the components of a mixture using a column of suitable adsorbent packed in a glass tube, as shown in the figure below. The mixture is placed on the top of the column, and an appropriate eluant is made to flow down the column slowly. Depending upon the degree of adsorption of the components on the wall adsorbent column, the separation of the components takes place. The component with the highest absorptivity is retained at the top, while the other flow down to different heights accordingly.
Thin layer chromatography
In this process the mixture of substances is separated into its components with the help of a glass plate coated with a very thin layer of adsorbent, such as silica gel and alumina, as shown in the figure below.
The plate used for this process is known as chrome plate. The solution of the mixture to be separated is applied as a small spot at a distance of 2 cm above one end of the plate. The plate is then placed in a closed jar containing a fluid termed as an eluant, which then rises up the plate carrying different components of the mixture to different heights.
Partition chromatography
In this process, a continuous differential partitioning of components of a mixture into a stationary phase and mobile phase takes place.Paper chromatography is a type of partition chromatography. A special quality paper known as chromatography paper is used. In this process, chromatography paper is used as a stationary phase which is suspended in a mixture of solvents that act as a mobile phase. Here, we put a spot at the base of the chromatographic paper with the mixture to be separated and as the solvent rises up this paper, the components are carried to different degrees depending upon their retention on the paper. The components are thus separated at different heights.
| Exam | Chapter |
| JEE MAIN | Purification and Characterisation of Organic Compounds |
Chromatography technique is used to
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A chromatography column, packed with silica gel as a stationary phase, was used to separate a mixture of compounds consisting of (A) benzamide (B) aniline, and (C) acetophenone. When the column is eluted with a mixture of solvents, hexane: ethyl acetate (20:80), the sequence of obtained compounds is:
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Using the provided information in the following paper chromatogram:
the calculated value of A ______
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In chromatography technique, the purification of compound is independent of :
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Given below are two statements :
Statement I: The retardation factor can be measured in meters/centimeters.
Statement II: value of the compound remains constant in all solvents.
Choose the most appropriate answer from the options given below :
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Which one of the following techniques is not used to spot components of a mixture separated on thin layer chromatographic plate?
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The separation of two coloured substances was done by paper chromatography. The distances travelled by solvent front, substance and substance
from the base line are
and
respectively. The ratio of
values of
to
is _________.
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Given below are two statements : One is labelled as Assertion and the other is labelled as Reason
Assertion : Thin layer chromatography is an adsorption chromatography.
Reason : A thin layer of silica gel is spread over a glass plate of suitable size in thin layer chromatography which acts as an adsorbent.
In the light of the above statements, choose the correct answer from the options given below
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Which of the following statements is not true about partition chromatography ?
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In Chromatography, which of the following statements is INCORRECT for ?
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Which technique among the following, is most appropriate in the separation of a mixture of of
-nitrophenol and picric acid?
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Following chromatogram was developed by adsorption of compound 'A' on a 6 cm TLC glass plate.
Retardation factor of the compound 'A' is______
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Match items of column I and II
Correct match is
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From the figure of column, chromatography given below, identify incorrect statements.
A. Compound ‘c’ is more polar than ‘a’ and ‘b’
B. Compound ‘a’ is least polar
C. Compound ‘b’ comes out of the column before ‘c’ and after ‘a’
D. Compound ‘a’ spends more time in the column
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Using column chromatography mixture of two compounds ‘A’ and ‘B’ was separated. ‘A’ eluted first, this indicates ‘B’ has
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Thin layer chromatography of a mixture shows the following observation :
The correct order of elution in the silica gel column chromatography is
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Three organic compounds A, B and C were allowed to run in thin layer chromatography using hexane and gave the following result (see figure). The value of the most polar compound is ______________
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Which of the following statement is correct for paper chromatography?
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Number of correct statements related to chromatography
1) Various terms such as stationary Phase, mobile phase & elution are related to chromatography
2) $R_f$ value is always less than 1
3) Solubility property is used in column chromatography.
4) Chromatography is derived from word "Kroma" means color.
5) Elution is based on differential adsorption
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Chromatographic technique/s based on the principle of differential adsorption is/are
A. Column chromatography
B. Thin layer chromatography
C. Paper chromatography
Choose the most appropriate answer from the options given below:
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On a thin layer chromatographic plate, an organic compound moved by $3.5 \mathrm{~cm}$, while the solvent moved by 5 $\mathrm{cm}$. The retardation factor of the organic compound is________ $\times 10^{-1}$.
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Adsorption' principle is used for which of the following purification method ?
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Chromatography is an important technique extensively used to seperate mixtures into their components, purify compounds and also to test the purity of compounds.
