HPLC Methodologies

Question 1

What is normal phase chromatography?

Answer 1

solute is adsorbed on the surface of the SP (polar interactions are dominant)

Question 2

The SP in NPC is

Answer 2

polar (silica gel or alumina backbone)

Question 3

MP in NPC is

Answer 3

relatively non-polar compared to SP (hexane mixed with polar solvent such as ether or ethyl acetate)

Question 4

What is reversed phase chromatography?

Answer 4

solute equilibrate in “in” and “out” of the liquid SP

Question 5

What is SP in LLC?

Answer 5

non-polar liquid coated on solid support (silica or polymer backbone)

Question 6

What is MP in LLC?

Answer 6

relatively polar compared to SP (water with relatively non-polar solvent such as acetonitrile)

Question 7

What is ion-exchange chromatography?

Answer 7

solute competes with the MP counter ions (of same charge as solute) for the fixed charge on SP
separates based on charge, hydration and size

Question 8

What is SP in IEC?

Answer 8

silica or polymer backbone containing anion exchange groups or cation exchange groups

Question 9

What is MP in IEC?

Answer 9

counter ions (inorganic salts or buffers)

Question 10

What is Gel permeation chromatography?

Answer 10

separates molecules based on size (pores)

Question 11

What is SP in GPC?

Answer 11

10 um particles with uniform pores

Question 12

What is MP in GPC?

Answer 12

liquid aqueous solvent or organic solvent

Question 13

What is gel filtration?

Answer 13

hydrophilic packing, separates polar species

Question 14

What is gel permeation?

Answer 14

hydrophobic packing, separates non polar species

Question 15

What is the relationship between polarity and elution times in NPC?

Answer 15

most polar solute elutes last

increasing polarity of MP decreases elution time

Question 16

What is the relationship between polarity and elution times in RPC?

Answer 16

most polar solute elutes first

Decreasing polarity of MP decreases elution time

Question 17

Competition model assumes ______

Answer 17

entire SP is covered by MP molecules
retention occurs during adsorption process
competition between solute molecules and MP molecules for A.S. on SP

Question 18

Solvent interaction model

Answer 18

retention results from the interaction of solutes molecules with the secondary layer of MP molecules, no interaction with SP

Question 19

Solvophobic model

Answer 19

retention is due to hydrophobic interaction between solute and MP

Question 20

Partitioning model

Answer 20

solute is fully embedded in the SP rather than adsorbed on the surface of SP

Question 21

What does the higher epsilon value mean?

Answer 21

the greater the strength of the solvent which results in faster elution or lower retention of solutes

Question 22

Solvent strength is ______________ to elutropic series (epsilon).

Answer 22

Directly proportional