Gas Chromatography Principle and Theory; Question and Answers For GPAT, GATE, Pharmacist, Drug Inspector Exams

Introduction :-

Gas Chromatography is an analytical technique use for separation of thermally stable and volatile substance.

In Gas Chromatography the mobile phase is gas and the stationary phase is solid or liquid.

Principle :-

The principle involved in gas Chromatography is adsorption or partition which is dependent on the stationary phase used.

If the stationary phase used is liquid it is called as gas liquid Chromatography (GLC).

In GLC mostly kiesulghur or diatomaceous earth.

If the stationary phase is solid it is called as gas solid Chromatography ( GSC).

In GSC mostly granular silica, alumina are used as stationary phase.

The components which is having lesser affinity to ward s.p travel faster and of greater affinity is travel slowly.

Theory :-

In this technique the sample is to be vapourised and is carried a long a prepared column of suitable temperature by means of a carrier gas which act as mobile phase.

When the vapour of the sample is passed through the column the components are separated by adsorption or partition basing on the stationary phase used.

The sample to be analysed by G.C. should be stable when vapourised and when passed through prepored or packed column in order to avoid decomposition of components and complex chromatogram if unstable or non volatile components are to be separated by G.C by preparing their derivatives.

Example :- Trimethyl silyl derivatives of carbohydrates.

Due to limited availability of solid adsorbent gas solid Chromatography is not widely used.

In gas liquid Chromatography the stationary liquid phase is located on a solid support or the wall of capillary tube.

The stationary phase used in GLC should have low vapour pressure at the column temperature and almost non volatile.

MCQ.

1. Which method is used to separation of thermally stable and volatile substance ?

A. NMR

B. Mass sepctroscopy

C. HPLC

D. Gas Chromatography.

2. Which sentence is true about gas Chromatography ?

A. It has gaseous stationary phase.

B. It is not used to volatile substance.

C. It is work on principal of the adsorption and partitions.

D. When stationary phase is liquid it is called a GSC

3. Which liquid are used in GLC ?

A. Kiesulghur

B. Diatomaceous earth

C. A and B

D. None of the above

4. Which solid are used in GSC ?

A. Alumina

B. Carbon

C. Granular silica

D. All of the above

5. In GLC, which condition is not suitable for stationary phase?

A. Low vapour pressure

B. Non volatile

C. A and B

D. None of the above

Answer key :-

1. D

2. C

3. C

4. D

5. D

REFERENCE

TEXT BOOK OF PHARMACEUTICAL ANALYSIS THIRD EDITION OF DR. RAVI SANKAR (17.1 TO 17.20)

TEXT BOOK OF PHARMACEUTCAL ANALYSIS FOUR EDITION OF DAVID.G.WATSON (261-290)