Chapter 25, Problem 25.27P

a)

Interpretation Introduction

Interpretation:

The ways to measure k and resolution has to be given.

Concept Introduction:

Resolution:

The resolution can be calculated using the formula as given below,

$\text{Resolution}\text{=}\frac{\sqrt{N}}{4}\times \frac{\alpha -1}{\alpha }\times \left(\frac{k}{1+k}\right)$

Where,

$N$ is the plate number

$\alpha$ is the relative retention

$k$ is the retention factor

Retention factor:

The time that is necessary to elute that peak minus the minimum possible time for the travel of unretained solute through the column is called as retention factor. The retention factor is calculated using the equation,

$\text{k=}\frac{{\text{t}}_{\text{r}}{\text{-t}}_{\text{m}}}{{\text{t}}_{\text{m}}}$

Where,

${\text{t}}_{\text{r}}$ = retention time

${\text{t}}_{\text{m}}$ = minimum possible time for the travel of unretained solute through the column.

b)

Interpretation Introduction

Interpretation:

The three methods for measuring ${\text{t}}_{\text{m}}$ in reversed-phase chromatography has to be stated.

Concept Introduction:

Reversed-phase chromatography:

One of the most common mode of HPLC is the reversed-phase chromatography.  In reversed-phase chromatography, the mobile phase is more polar and the stationery phase is nonpolar or weakly polar.  The solute is more rapidly eluted from the column in reversed-phase chromatography as the mobile phase is polar.  Less polar mobile phase (solvent) has a high mobile phase strength.

This method is adequate to separate mixtures of low molecular mass.

c)

Interpretation Introduction

Interpretation:

The three methods for measuring ${\text{t}}_{\text{m}}$ in hydrophilic interaction liquid chromatography has to be stated.

Concept Introduction:

Hydrophilic interaction liquid chromatography (HILIC):

This is other technique to separate small polar compounds on stationary phase with polar nature. It has reported as variant of normal phase liquid chromatography, but the mechanism of separation in HILIC is more complicated than in normal phase liquid chromatography. Bare silica or silica gels modified with polar functional groups are generally used as HILIC stationary phase. Polymer-based stationary phases would also be used.

d)

Interpretation Introduction

Interpretation:

The ${\text{t}}_{\text{m}}$ of the particle size has to be calculated.

Concept Introduction:

The formula, $t_m\approx \frac{L{d}_c^2}{\left(2F\right)}$ can used to calculate ${\text{t}}_{\text{m}}$ . Here L is the length of the column (in cm), ${\text{d}}_{\text{c}}$ is the diameter of the column (in cm) and F is the rate of flow (ml/min).