Chapter 26, Problem 26.20QAP

Interpretation Introduction

(a)

Interpretation:

In order to obtain desired resolution of 1.5, the number of plates should be calculated.

Concept introduction:

The resolution can be calculated as follows:

$\begin{array}{l}R=\frac{{\left(t_R\right)}_B-{\left(t_R\right)}_A}{{\left(t_R\right)}_B}\times \frac{\sqrt{N}}{4}\\ 4R\times \frac{{\left(t_R\right)}_B}{{\left(t_R\right)}_B-{\left(t_R\right)}_A}=\sqrt{N}\\ N={\left[4R\times \frac{{\left(t_R\right)}_B}{{\left(t_R\right)}_B-{\left(t_R\right)}_A}\right]}^2\\ \text{where:}\\ \text{N=Number}\text{of}\text{plates}\\ {\left({\text{t}}_{\text{R}}\right)}_{\text{A}}\text{,}{\left({\text{t}}_{\text{R}}\right)}_{\text{B}}\text{=Retention}\text{times}\text{of}\text{species}\text{A}\text{and}\text{B}\text{respectively}\\ \text{R=Resolution}\end{array}$

Interpretation Introduction

(b)

Interpretation:

Height of the column should be calculated.

Concept introduction:

The plate height can be calculated as follows:

$\begin{array}{l}H=\frac{L}{N}\\ \text{where:}\\ \text{H=Plate}\text{height}\\ \text{L=Length}\text{of}\text{column}\text{packing}\\ \text{N=Number}\text{of}\text{plates}\end{array}$

Interpretation Introduction

(c)

Interpretation:

Retention time of the methylcyclohexene should be calculated.

Concept introduction:

Retention time is directly proportional to the resolution. Therefore, following equation can be used.

$\frac{{\left(t_R\right)}_1}{{\left(t_R\right)}_2}=\frac{{\left(R\right)}_1^2}{{\left(R\right)}_2^2}$