Column Chromatography-Characteristics and Development Technique Part 2

Column characteristics :-

The length: diameter ratio of column is 10:1 to 30:1.

The length of the column is depend upon

  • Affinity of compound towards the adsorbent used.
  • Number of compound to be separated.
  • Type of adsorbent used.
  • Quantity of the sample.

] :-

A column can be packed by two Method

A. Wet packing :- the column is suported in a vertical position and a slurry of the adsorbent in suitable solvent is poured through out the top open end. It is allowed to settle under gravity until column of the desired height is obtained.

B. Dry packing :- After viewing the suitable activity or grade, powered adsorbent is transferred to the column tubing. Vacuum is applied at the bottom of the column and is tapped with a suitable object like wooden or plastic rod.

For better separation, sample/ adsorbent ratio should range from 1:20-1:100.

Smaller particle  of adsorbent can be useful in packing column.

 Introduction of the sample :-

The sample which is usually a mixture of components is dissolved in m.p. and introduce in top of column and individual sample can be separated by a process of Elution.

Development Technique :-

After the introduction of the sample by Elution technique, the individual components are separated out from the column.

The two technique are

1. Isocratic Elution technique :-

In this Elution technique the same solvent composition or solvent of same polarity is used through out the process of separation. Eg. Petroleum ether : benzene =1:1.

2. Gradient elution technique :-

In this Elution technique solvent are gradually increase polarity or increase Elution strength are used during the process of separation.

Eg. Initially benzene then chloroform.

Detection of components :- 

The separated components can be detected visually if they are colour.

The coloured band are observed in the column moving down separately and can be collected separately.

MCQ

1. The length and diameter of the column Chromatography is which are false option ?

A. 10:1

B. 10:2

C. 10:3

D. 10:4

2. In which factor of column Chromatography is not affecting by the length of the column ?

A. Affinity of compound towards the adsorbent used.

B.Number of compound to be separated.

C.Type of adsorbent used.

D. Decreased separation rate.

3. How many development technique are seen in column Chromatography?

A. One

B..Two

C. Three

D. Four

4. In gradient elution technique which is true

A. Polarity is increase

B. Polarity is decrease

C. Polarity is gradually increase

D. Polarity is sudden increase.

5. Isocratic Elution M.P and sample have

A. Different polarity

B. Same polarity

C. One have more and second have less

D. All of the above

Answer key

1. D

2. D

3. B

4. C

5. B

Reference take in text book of p.analysis of third edition Dr.s.ravi sankar(13.4 TO13.13)

 

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