column chromatography lab

Question 1

increase polarity of eluent

Answer 1

when components have different rf values and the second one really isnt moving
-only change it when the first sample is out

Question 2

polar sample

Answer 2

lower rf value and slower run

Question 3

nonpolar sample

Answer 3

out of the column first

Question 4

hexane

Answer 4

non polar

Question 5

slurry

Answer 5

silica mixed with eluent
-it is exothermic
-bubbles may come when packing because the solvent is boiling
-the absorbent
-must always be wet

Question 6

air bubble

Answer 6

interfere with results because the sample run faster since the bubbles dont have the polar surfacee that the silica gel has
-dont let stationary and mobile phase equilibrate

Question 7

dry absorbent

Answer 7

bad
-will cause cracking and uneven bands/ overlap in tlc

Question 8

dissolve sample

Answer 8

using eluent

Question 9

sample left in the sand layer when running the eluent

Answer 9

will get too diluted and are useless
-will be impossible to separate

Question 10

ideal rf for separation

Answer 10

.35

Question 11

ideal rf between samples

Answer 11

.2

Question 12

sand

Answer 12

is used to tightly pack and level silica
and to apply an eve layer of pigement and not disturb silica while adding pigment

Question 13

air pressure

Answer 13

can be used to pack column and speed up elution

Question 14

small sample

Answer 14

used a pipette instead of a column

Question 15

before addition of slurry

Answer 15

add eluent to wet the column

Question 16

cotton/ wool

Answer 16

used to keep the silica in the column/ filter all solution leaving the column

Question 17

adding slurry

Answer 17

add a little, level it (let is travel to sit on the sand), then add the rest as you drain the eluent, then sand on top of silica

Question 18

adding pigment

Answer 18

slowly and an even layer over the sand and let the sand absorb all of it before running the eluent
-add eluent and drain till it is all through

Question 19

eluent should never

Answer 19

go below top layer of sand bc it may cause air bubbles/ unevenness= poor separation

Question 20

uneven bands

Answer 20

poor separation at TLC/ collected fractions wont be pure

Question 21

dissolving sample/ spinach

Answer 21

with the very least bit of eluent

Question 22

pigments completely through the sand

Answer 22

add more eluent, prep test tubes, and run the fractions
-half volume of test tubes

Question 23

decreasing rf values/ nonpolar to polar

Answer 23

-carotenes (yellow organge)
-pheophytin alpha (gray)
-pheophytin beta (gray) (may not be visible)
-chrolopyll alpha (blue green)
-chlorophyll beta (green)
-xanthophylls (yellow)

Question 24

why do pigments travel at different rates

Answer 24

polarity
-polar pigments interact with polar stationary phase and stay there longer

Question 25

increasing mobile polarity

Answer 25

makes all samples move faster

Question 26

initial green pigment line

Answer 26

will separate into yellow and green (yellow is faster)