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Medchem 423 > Chromatgraphy > Flashcards

Flashcards in Chromatgraphy Deck (12)
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1

1. Distinguish between the different types of chromatography presented herein; understand the current applications of each (if any)

a. Thin layer chromatography

● Thin layer chromatography
○ Most common form
○ Stationary phase is coated on a sheet of glass, metal, or plastic in a thin layer
○ Analytes are spotted on the plate which is placed in a chamber containing solvent
and the mobile phase will travel up the plate by capillary action

2

1. Distinguish between the different types of chromatography presented herein; understand the current applications of each (if any)

b. column chromatography

● Column chromatography
○ The stationary phase is packed into the column and the mobile phase passes through the column and drips out on the bottom
○ The mobile phase will try to pull the compounds with it depending on how strongly the compounds interact with both the stationary and mobile phase

3

1. Distinguish between the different types of chromatography presented herein; understand the current applications of each (if any)

c. High Performance Liquid Chromatography (HPLC)

● High performance liquid chromatography (HPLC)
○ Same concept as column chromatography but using higher pressure to push
solvents through the column
○ Deals with smaller compound sizes

4

1. Distinguish between the different types of chromatography presented herein; understand the current applications of each (if any)

D. Gas chromatography

● Gas chromatography
○ Mobile phase is a gas and thus is limited to anaytes stable in the gas phase
○ Mobile phase is passed through the column by pressure (a pump)
○ Gas chromatography used for smaller, non polar molecules whereas liquid
chromatography is used for larger, more polar compounds

5

1. Distinguish between the different types of chromatography presented herein; understand the current applications of each (if any)

Gel permeation

● Gel permeation/size exclusion chromatography
○ Separates the molecules based on their size
○ The smaller molecules will enter the pores of the beads whereas the larger molecules are excluded from the pores
○ The larger compounds will elute first because they have no interaction with the beads

6

2. Understand the basic functioning of an HPLC system (what is the function of each part)

● Injection port- used to place sample into machine
● Mobile phase- supplies the substance that will run over the column
● Controller- tells the pump what to do
● Pumps- pump solvent through the column using high pressure
● Column- where the sample is tubed into and separated
● UV detector- detects the compounds as they come off of the column
● Degasser- takes the air out of the solvents
● Autosampler- allows you to run a lot of samples back to back, can set it to run a certain
amount of samples so you do not have to manually keep running them

7

3. Predict the order of elution of analytes in reversed-phase and normal-phase chromatography separations

● Normal- phase→
the stationary - polar and hydrophilic while the mobile phase is hydrophobic
○ Because the stationary phase is polar, polar compounds will interact more with the column and thus elute last
○ Mobile - nonpolar - hydrophobic compounds will elute first because they will not react as much with the stationary phase but will react more with the mobile phase

● Reversed-phase→
the stationary - nonpolar and hydrophobic while the mobile phase is hydrophilic
○ Because the stationary phase is nonpolar, nonpolar compounds will interact more with the column and elute last
○ The more polar compounds will elute first because they will not react as much with the stationary phase but will react more with the mobile phase

8

4. Understand and be able to predict the types of interactions that analytes can have with a given stationary phase

● Just different hydrophobic and hydrophilic interactions

● Hydrogen bonding, van der waals interactions, pi-pi stacking

9

5. Understand the effects of changing a mobile phase on the separation of molecules in a chromatographic experiment

● Changing the mobile phase will cause the molecules to elute differently

● Polar mobile phases (highest solvent strength to lowest):
○ Methanol
○ Acetonitrile
○ water

● Nonpolar mobile phases (highest solvent strength to lowest):
○ Isopropanol
○ Ethyl acetate
○ Chloroform
○ Dichloromethane
○ hexanes

● The mobile phase can affect how much band broadening you have
● To get compounds to separate better, use a STRONGER solvent/mobile phase→ move
up the list to pick a stronger one

10

1. Understand the central concept of each different type of spectroscopy: the manner in which energy interacts with your sample

● X-ray crystallography

○ A wave will bend around an object in its path, x-rays bend around electron clouds
of atoms

○ A crystal is made up of repeating patterns of atoms. The crystal is rotated and the
scattering of light is computed

○ Strength:​ possible to determine entire structure including relative or absolute
stereochemistry of small molecules

○ Weakness​: crystallization process is laborious, certain classes of molecules aredifficult/nearly impossible to crystallize

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spectroscopy

interaction of energy with matter

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chromophore

functional group that absorbs UV visible light