Question

26-D. Consider a capillary electrophoresis experiment conducted near pH9, at which the electroosmotic flow is stronger than the electrophoretic flow.

(a) Draw a picture of the capillary, showing the placement of the anode, cathode, injector, and detector. Show the direction of electroosmotic flow and the direction of electrophoretic flow of a cation and an anion. Show the direction of net flow.

(b) Using Table 15-1, explain why ${\mathbf{CI}}^{\mathbf{-}}$has a shorter migration time than ${\mathbf{I}}^{\mathbf{-}}$Predict whether ${\mathbf{Br}}^{\mathbf{-}}$will have a shorter migration time than ${\mathbf{CI}}^{\mathbf{-}}$or a greater migration time than ${\mathbf{I}}^{\mathbf{-}}$

(c) Why is the mobility of ${\mathbf{I}}^{\mathbf{-}}$greater than that of${\mathbf{CI}}^{\mathbf{-}}$?

Short answer

a) The pictures of electrophoretic and electro osmotic process with anode, cathode, injector, detector, and flow was drawn

b) The increasing order of migration time of given ions is,$\underset{}{\mathrm{Cr}<{\mathrm{I}}^{-}<\mathrm{Br}}$

c) mobility of${\mathrm{CI}}^{-}$ is lower mobility than${\mathrm{I}}^{-}$

Step-by-step solution

Interpretation and introduction:

(a) Interpretation Introduction

Interpretation:

The pictures of electrophoretic and electro osmotic process with anode, cathode, injector, detector, and flow should be drawn.

Concept introduction:

Electrophoresis:

The movement of charged particles due to the applied electrical field is known as electrophoresis.

Electro osmosis:

The movement of charged medium due to the applied electrical field is known as electrophoresis.

STEP:2 : Show direction of electroosmotic flow and the direction of electrophoretic flow

To draw the pictures of electrophoretic and electro osmotic process with anode, cathode, injector, detector, and flow.

In the above figure 1 shows the anode, cathode, injector, detector, and flow of the electrophoretic and electro osmotic processes.

The pictures of electrophoretic and electro osmotic process with anode, cathode, injector, detector, and flow was drawn.

(b) Interpretation Introduction

Interpretation:

The migration times of ${\mathrm{CI}}^{-}$,${\mathrm{I}}^{-}$ , and${\mathrm{Br}}^{-}$ should be comparatively explained.

Concept introduction:

Electrophoresis:

The movement of charged particles due to the applied electrical field is known as electrophoresis.

Electro osmosis:

The movement of charged medium due to the applied electrical field is known as electroosmosis.

lonic mobility:

The tendency of ionic movement that respect with a unit current is given by the ionic mobility.

STEP:3-Explanation of Solution:

To comparatively explain the migration times of ${\mathrm{CI}}^{-}$,${\mathrm{I}}^{-}$ , and${\mathrm{Br}}^{-}$

From the standard data the mobility of ${\mathrm{Cl}}^{-}$,${\mathrm{l}}^{-}$ , and S${\mathrm{Br}}^{-}$ are,

Mobility of${\mathrm{Cl}}^{-}$ is $7.91\times {10}^{-8}$

Mobility of ${\mathrm{Br}}^{-}$is $8.13\times {10}^{-8}$

Mobility of ${\mathrm{l}}^{-}$is $7.96\times {10}^{-8}$

Here,${\mathrm{Br}}^{-}$ I' has greater mobility than${\mathrm{Cl}}^{-}$ and the electro osmosis force opposes the mobility of${\mathrm{l}}^{-}$ ion so it is eluted later than${\mathrm{Cl}}^{-}$

Here, has greater mobility than${\mathrm{l}}^{-}$ and the electro osmosis force is opposes the mobility of${\mathrm{Br}}^{-}$ ion so it is eluted later than ${\mathrm{l}}^{-}$.

Therefore, the increasing order of migration time of given ions is,

$\underset{�}{\mathrm{Cr}<{\mathrm{I}}^{-}-<\mathrm{Br}}$

STEP:4-Conclusion:

The migration times of ${\mathrm{CI}}^{-}$,${\mathrm{I}}^{-}$ , and${\mathrm{Br}}^{-}$ were comparatively explained.

c)To comparatively explain the migration times of ${\mathrm{Cl}}^{-}$, ${\mathrm{l}}^{-}$, and${\mathrm{Br}}^{-}$

From the standard data the mobility of , \, and are,

Mobility of${\mathrm{Cl}}^{-}$ is$7.91\times {10}^{-8}$

Mobility of${\mathrm{Br}}^{-}$ is$8.13\times {10}^{-8}$

Mobility of${\mathrm{l}}^{-}$ is$7.96\times {10}^{-8}$

Here,${\mathrm{l}}^{-}$ has greater mobility than${\mathrm{Cl}}^{-}$ and the electro osmosis force is opposes the mobility of${\mathrm{l}}^{-}$ ion so it is eluted later than${\mathrm{Cl}}^{-}$

The size of${\mathrm{l}}^{-}$ is bigger than${\mathrm{Cl}}^{-}$ so result of this the charge density of${\mathrm{Cl}}^{-}$ is higher than${\mathrm{l}}^{-}$ and${\mathrm{l}}^{-}$ has lower hydrated radius than${\mathrm{Cl}}^{-}$therefore the mobility of ${\mathrm{Cl}}^{-}$is lower mobility than${\mathrm{l}}^{-}$