Chapter 20, Problem 8Q

Interpretation Introduction

Interpretation:

The corrected $\text{mol}\text{\%}$ for compound 1 and 2 in the mixture is to be calculated.

Concept introduction:

Gas chromatography is efficiently used for the compounds that have high vapor pressures which allow them to pass through a GC column.

A gas chromatography does not identify compounds if unknown samples are loaded into the column. GC is one of type of partition chromatography, where the sample that has to be analyzed get adsorbed on the stationary phase.

The stationary phase is formed by high boiling nonvolatile liquid, usually a polymer. An inert gas like helium or nitrogen is utilized to form mobile phase. In GC, no interaction of compound with mobile phase occurs, unlike LC and TLC. The inert gas that makes the mobile phase carries the compound down the column when it is in vapor state. The compounds present in the mixture divide themselves between the gas phase and the liquid phase in the column in an equilibrium.

The components of gas-liquid chromatography are as follows:

• High-pressure pure carrier gas source
• Flow controller
• Heated injection port
• Column and column oven
• Detector
• Recording device or data station

Gas-liquid chromatography is very useful for the quantitative determinations of the components in volatile mixtures. The comparison of peak areas on the chromatogram results in the determination of amounts of the compounds. The area under the chromatographic peak is proportional to the concentration of the sample responsible for it denoted by response factor given as follow:

  $A=f\text{C}$

Where,

• $A$ is area under chromatographic peak.
• $f$ is response factor.
• $\text{C}$ is concentration of sample.

In chromatographic analyses, the samples that contain more than 1 component so, relative response factors of one compound to the other compounds in the sample are determined.

The relative response factor is given by ${\text{M}}_{\text{f}}$ which is calculated as follows:

  $M_{\text{f}}=\frac{{\text{f}}_{\text{1}}}{{\text{f}}_{\text{2}}}$

Where,

• $f_{\text{1}}$ is $\frac{A_{\text{1}}}{{\text{C}}_{\text{1}}}$ .
• $f_2$ is $\frac{A_2}{{\text{C}}_2}$ .