Question

List the types of substances to which each of the following chromatographic methods is most applicable:

(a) gas-liquid

(b) liquid adsorption

(c) liquid-liquid partition

(d) reversed-phase partition

(e) ion exchange

(f) gel permeation

(g) gas-solid

(h) gel filtration

(i) ion-pair

Short answer

a) The volatile and thermally stable substances are used for gas-liquid chromatography.

b) The nonpolar polymers and isomeric compounds of low molecular weight are used in liquid adsorption chromatography.

c) The amino acids, glycosides and carbohydrates are used in liquid-liquid partition chromatography.

d) The thermally unstable and non-volatile organic substances are used in reversed-phase chromatography.

e) The ionic compounds are used in ion-exchange chromatography.

f) The gel permeation chromatography is used substances of high molecular weight and soluble in nonpolar solvent.

g) The substances of non-volatile and low molecular mass gas are used in gas-solid chromatography.

h) The molecules of high molecular mass and hydrophilic nature are used in gel filtration chromatography.

i) The small ionic organic and inorganic substances are used in ion-pair chromatography.

Step-by-step solution

Part (a) Step 1: Given Information

The type of substance to which gas-liquid chromatography is most applicable is to be stated.

Part (a) Step 2: Explanation

The gas-liquid chromatography is used, when the substance is in the mixed form of gas and liquid. The substances that are volatile and thermally stable is used in gas liquid chromatography.

Part (b) Step 1: Given Information

The type of substance for liquid adsorption chromatography is to be stated.

Part (b) Step 2: Explanation

The substances that absorbed the other substance are called adsorbent substance. The liquid adsorption chromatography uses the quantity absorbed by the adsorbent. The different layer of absorbed substance is contained in the liquid adsorption chromatography. The nonpolar polymers and isomeric compounds of low molecular weight are used in liquid adsorption chromatography.

Part (c) Step 1: Given Information

The type of substance for liquid-liquid partition chromatography is to be stated.

Part (c) Step 2: Explanation

The non-volatile and thermally unstable substances like amino acids, glycosides and carbohydrates are used in liquid-liquid partition chromatography.

Part (d) Step 1: Given Information

The type of substance for reversed-phase chromatography is to be stated.

Part (d) Step 2: Explanation

The molecules of the mobile phase absorb the molecules of the hydrophobic stationary phase, and hydrophilic molecules pass from the mobile phase. The thermally unstable and non-volatile organic substances are used in reversed-phase chromatography.

Part (e) Step 1: Given Information

The type of substance for ion exchange chromatography is to be stated.

Part (e) Step 2: Explanation

The affinity of ion exchange is more so ionic compounds of high molecular mass are used in ion-exchange chromatography.

Part (f) Step 1: Given Information

The type of substance for gel permeation chromatography is to be stated.

Part (f) Step 2: Explanation

The larger size molecule remains for less time in pores of gel so they get separated very easily. The material of high molecular weight and soluble in nonpolar solvent are used in gel permeation chromatography.

Part (g) Step 1: Given Information

The type of substance for gas-solid chromatography is to be stated.

Part (g) Step 2: Explanation

The molecules of the gaseous substance whose size is smaller than the pore size of solid surface easily passed from the pores. The molecules of size greater than the pore size of solid surface separated from the solid surface. The substances of non-volatile and low molecular mass gas are used in gas-solid chromatography.

Part (h) Step 1: Given Information

The type of substance for gel filtration chromatography is to be stated.

Part (h) Step 2: Explanation

The porous matrix of gel acts as a stationary phase and the substance to be separated acts as a mobile phase. When molecules of a smaller size than porous matrix passes, they get easily passed and molecules of size greater than porous matrix get separated.

Part (i) Step 1: Given Information

The ionic compounds used in ion-pair chromatography is to be stated.

Part (i) Step 2: Explanation

The substance in ion-pair chromatography separated in anions and cations on the basis of their polarity. Two different mechanisms can be used to separate the ions in the substance. In the first mechanism, unchanged ion pair with solute ion pair in the mobile phase is portioned into a nonpolar stationary phase. In the second mechanism, separation takes place between the neutral stationary phase and the charged mobile phase.