Chapter 22, Problem 22.1P

(a)

Interpretation Introduction

Interpretation:

Difference between wall-coated, support-coated, and porous-layer open tubular columns for gas chromatography has to be explained.

Concept Introduction:

In analytical chemistry, gas chromatography is an important tool for the separation and identification of those compounds which can be vaporized without decomposition. Gas chromatography may also be used to prepare pure compounds from mixture. In GC, mobile phase is a carrier gas. Mostly helium or unreactive gas like nitrogen is used as carrier gas. Stationary phase is a microscopic layer of solid or liquid polymer.

Explanation of Solution

In wall-coated open tubular column, liquid stationary phase is bonded to the wall of column. In support-coated open tubular column, liquid stationary phase is bonded to solid support on wall of column.

While porous layer open tubular column, solid stationary phase is bonded to wall of column.

(b)

Interpretation Introduction

Interpretation:

Advantage of bonded stationary phases in the gas chromatography has to be explained.

Concept Introduction:

Refer to part (a).

Explanation of Solution

Bonded or cross linked stationary phase reduces the tendency of the tendency for the stationary phase to bleed from the column during the entire process.

(c)

Interpretation Introduction

Interpretation:

Use of makeup gas in for some gas chromatography detectors has to be explained.

Concept Introduction:

Refer to part (a).

Explanation of Solution

Makeup gas is used in gas chromatography to sweep the components through a detector to minimize the band broadening.

(d)

Interpretation Introduction

Interpretation:

Work of solvent trapping and cold trapping in splitless injection has to be explained.

Concept Introduction:

Refer to part (a).

Explanation of Solution

In solvent trapping, initial column temperature is low enough to condense solvent at the beginning of the column. Solute is very soluble in the solvent and is trapped in a narrow band at the start of the column.

In cold trapping, initial column temperature is around ${150}^{\circ }\text{C}$ lower than the boiling points of solutes, which condense in a narrow band at the start of the column.

In both cases, elution occurs as the column temperature is raised.