chromatography quiz

Question 1

purpose of thin layer chromatography

Answer 1

assess actual number of chemicals in a compound
(# of spots = number of chemicals)

Question 2

4 characteristics of a quality TLC plate

Answer 2

1. small spot circumferences
2. range of sample applications with sample spotted 1x, sample spotted 2x, and sample spotted 3x
3. penciled origin line before plate development and penciled solvent front at conclusion of plate development
4. don’t damage the caked on silica and handle the plate by its edges

Question 3

purpose of column chromatography

Answer 3

separate pigment chemical on the basis of pigment or molecular polarity and how each pigment binds to silica

Question 4

column chromatography stationary phase

Answer 4

silica (solid)

Question 5

column chromatography mobile phase

Answer 5

hexane or 95:5 hexane:ethyl acetate

Question 6

elute is to

Answer 6

drain

Question 7

gradient elution is to

Answer 7

increased polarity of mobile phase over course of experiment

Question 8

adsorb is to

Answer 8

surface sticking of pigment molecules to silica molecules

Question 9

end result of today’s work will give

Answer 9

at least 1 as high as 4 fractions or test tubes after CC and hopefully each fraction will have at least 1 spot

Question 10

objective of column chromatography work

Answer 10

to purify paprika extract on basis of molecular polarity

Question 11

determination of whether the column work was successful will take place next week and will consist of

Answer 11

TLC analysis of eluted test tube fractions

Question 12

slurry

Answer 12

slush or insoluble mix of silica in hexane

Question 13

1st major mistake to avoid when preparing a column

Answer 13

is to let the column run dry

Question 14

2nd major mistake to avoid when preparing a column

Answer 14

is after the paprika is applied to close stopcock

Question 15

too much silica slurry-packed into column

Answer 15

band diffusion

Question 16

too little silica slurry-packed into column

Answer 16

insufficient material to do polarity separation

Question 17

flow rate or elution rate or drip rate too fast

Answer 17

insufficient time to do polarity separation (i.e. the pigments aren’t interacting with silica to avoid separation)

Question 18

flow rate or elution rate or drip rate too slow

Answer 18

band diffusion

Question 19

order of elution

Answer 19

yellow elutes first
orange elutes second

Question 20

yellow =

Answer 20

carotene

Question 21

orange =

Answer 21

capsanthin

Question 22

why does orange elute AFTER yellow

Answer 22

has fewer O atoms