Unit 6

Question 1

What are 3 types of liquid chromatography?

Answer 1

1. paper
2. thin-layer
3. liquid column (LC)

Question 2

compare preparative LC vs analytical LC

a) objective
b) sample volume, column size, particle size
c) back pressure

Answer 2

analytical LC

• objective: identify and quantify target molecules
• small sample vol, column size, particle size
• higher back pressure (>50 bars)

prep LC

• purify and collect target quantities of molecules for future use
• large sample vol, column size, particle size
• low back pressure (<10bars)

Question 3

what are the main components to a HPLC system?

Answer 3

1. solvent enters pump then enters mixer
2. add sample
3. injection into HPLC column
4. enter into detector
5. production of chromatogram

Question 4

what are types of LC columns?

Answer 4

reverse phase
normal phase
ion exchange
size exclusion
affinity
chiral

Question 5

define reverse phase and normal phase chromatography

Answer 5

reverse phase: non-polar stationary phase and polar mobile phase

normal phase: polar stationary phase and non polar mobile phase

Question 6

smaller particles allows for what?

what is a drawback of this?

Answer 6

1. small theoretical plate height (H)
2. broader range of optimal flow rates

drawback: higher back pressure

Question 7

describe back pressure

Answer 7

difference between pressure of entrance vs the exit

Question 8

is bigger or smaller particles better? why?

Answer 8

smaller because it produces a flatter curve, which indicates better separation of compounds

thus at slower flow rates, there is higher efficiency of the column

Question 9

which should you use for integration of chromatographic peaks?

a) peak height
b) peak area

Answer 9

area b/c it is more accurate than height

Question 10

what is the function of 2D chromatograms?

Answer 10

instead of having chromatogram in one direction, it gives 2 directions of retention time

this allows for further separation within one peak, which may be the result of 2 different compounds