Chapter 22, Problem 22.3P

Interpretation Introduction

Interpretation:

Reason behind the thermal conductivity detector responds to all analytes except carrier gas has to be explained. Also, reason for flame ionization detector to be not universal has to be determined.

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.

The thermal conductivity detector measures changes in thermal conductivity of gases present in the column. Flame ionization detector burns the eluate in ${\text{H}}_{\text{2}}$ and ${\text{O}}_{\text{2}}$ flame to create the $\text{CH}$ radical, which then go on to be ionized to a small extent. Those ions are detected in the detector.