CE

Question 1

is CE a chromatography

Answer 1

no

Question 2

what is CE

Answer 2

• separation of charged analyte in applied electric field.
• while chromatography is separation based on distribution of two phase on different rate

Question 3

what is the challenge in CE

Answer 3

• joule heating: caused by the current flowing through the tube

Question 4

what components that affect heat

Answer 4

heat is proportional to applied electric field and diameter of the tube

Question 5

how does joule heating affect resolution

Answer 5

cause lost of resolution

Question 6

what is the possible solution for joule heating

Answer 6

• narrowing tune: because heat is proportion to the tube diameter

-less conducting buffer solution: to reduce current flowing through the tube.
- cold temperature

Question 7

how does capillary affects the separation

Answer 7

the short the capillary the first the separation

Question 8

what is the commonly used capillary material

Answer 8

fused silica

Question 9

what happens when pH of the buffer added is lower then the pKa of the silica

Answer 9

• this will cause silica surface / silanol group to be protonated or positively charged and we will have neutral capillary surface

Question 10

what happens when pH of the buffer added is higher then the pKa of the silica

Answer 10

• this will cause silica surface / silanol group to be de-protonated means they will release proton and this will cause excess positively charged in the capillary surface and negatively charge surface.

Question 11

what is the double layer of silica surface

Answer 11

i the formation of two layers
- immobilized layer: when proton bound to the negatively charged surface and do not mobile.
- diffuse layer: when ions are freely moving in the liquid near capillary wall.

Question 12

what is EOF (electroosmotic flow )

Answer 12

• is the net liquid flow to ward the cathode or
• applied potential along the capillary by electrode at the end of the capillary.

Question 13

what is the consequence of applied electrode

Answer 13

this will cause the excess cation to be attracted by the cathode.

Question 14

what is flat flow profile

Answer 14

is the flow mostly created near the capillary wall.

Question 15

why do we need to control EOF

Answer 15

because some application in the capillary require higher EOF and other requires lower EOF

Question 16

so how can we regulate the EOF/ solution on how to control EOF

Answer 16

we can regulate it according to the
- capillary material. by choosing capillary material that produce lower EOF at higher pH.
EX: pyrex
- buffer pH: because pH increase with increase of the EOF
- electric field applied along the capillary: by increasing the voltage we speed up the EOF.
- temperature: by increasing the temperature you lower the viscosity which increase EOF
- surfantact: when we add surfactant that interact with the charged silanol group at the wall will be mask the charges and neutralize them means we lower charges at the capillary wall with lower the EOF.

Question 17

how is the silica affected by the pH which will affect the EOF regulation

Answer 17

at acidic condition means lower pH silica surface is quite uncharged means less EOF but when the pH is increase the surface is deprotonated causing the increase of the EOF.

Question 18

what does separation in CE based on

Answer 18

ions in CE are moved based on charges and size

Question 19

what happens when EOF is greater than EP of anion

Answer 19

cation and anion can be analyzed together

Question 20

what is effective mobility

Answer 20

is resulting mobility of combined of two forms (charged and uncharged)

Question 21

by considering the formula of electrophoretic mobility how is it affected by charge, radius and viscosity

Answer 21

electrophoretic mobility increase with large charge of ion and decrease with increase of radius and viscosity.