Chapter 25 Capillary Elecrophoresis

Question 1

field strength and typical strength

Answer 1

separation power of electrophoresis

typical strength- 100-400 v/cm

Question 2

what is capillary electrophoresis and what types of cells can they analyze?

Answer 2

separates ions based on voltage (about 30kV) from end to end of a fused silica capillary tube
both single and whole cells

Question 3

what voltage do we apply on 75cm capillary to achieve 262 v/cm field strength?

Answer 3

E=v/l
E=262 v/cm L=75 c
v=19650…19.65 kV

** work in kV

Question 4

why not run at 1000 v/cm?

Answer 4

when it runs at an excessive field strength it generates heat in capillary and parabolic flow (laminar/hydrodynamic) is produced

Question 5

other words for parabolic flow

Answer 5

laminar/hydrodynamic

Question 6

why does a high field strength produce parabolic flow?

Answer 6

capillary dissipates heat in separation

molecules in cells in capillary move faster than walls and walls cannot get rid of heat

Question 7

how can joule heating be studied?

Answer 7

joule heating plot of current vs. applied voltage

Question 8

why do we use current for joule heating plot?

Answer 8

it is the easiest way to check if the separation is working or running smoothly…constant applied voltage should yield constant current

Question 9

what can joule heating plot tell us?

Answer 9

what maximum field strength to apply

Question 10

what are the units for currents inside CR?

Answer 10

micro amps (1x10^-6)

Question 11

what happens when there is a bubble inside of the capillary?

Answer 11

the current will drop because of a broken resistor

Question 12

what determines the species that comes out of the capillary?

Answer 12

analyte must be moving at velocity

velocity must be proportional to the total mobility and field strength

Question 13

total mobility of a chemical

Answer 13

sum of electrophoretic mobility and electroosmotic mobility

Question 14

electroosmotic flow and what is dependent on it

Answer 14

bulk flow

pH and capillary surface dependent …its controllable

Question 15

how do we separate a mixture of neutral analytes?

Answer 15

we add chemicals to the buffer that interacts or partitions with the neutral species
we use buffer additives (sodium dodecy sulfate (SDS))
these chemicals act as a psuedo stationary phase…induce partitioning within mobile phase

Question 16

what do surfactants do?

Answer 16

form sperical micells when used above threshold concentration

Question 17

what is a micelle?

Answer 17

spherical agrogate with polar head grroup on the exterior of sphere giving hydrophobic core and polar exterior

Question 18

E=V/L

Answer 18

V-applied voltage potential (vinlet-voutlet)

L-length of capillary (cm)