Chromatography

Question 1

What is the basic principle of chromatography?

Answer 1

The partitioning of analyses between a stationary phase and a mobile phase

Question 2

What happens to compounds with partition coefficient favouring the mobile phase?

Answer 2

They migrate faster than compounds that favour the stationary phase

Question 3

What is a eluent?

Answer 3

Mobile phase

Question 4

What is elution?

Answer 4

The motion of solute and solvent through the stationary phase

Question 5

What is effluent?

Answer 5

The mobile phase (and solute) collected at thread of the chromatography

Question 6

What is resolution?

Answer 6

The degree of separation

Question 7

What did the mobile phase move through the stationary phase via?

Answer 7

Capillary action

Question 8

What is the distance travelled by the analyte determined by?

Answer 8

It’s relative affinity for the stationary versus the mobile phase

Question 9

What is the stationary phase?

Answer 9

A plate (glass,plastic,aluminium) coated with adsorbent SiO2

Question 10

What percentage of weight volume of solvent is the sample dissolved in?

Answer 10

1-2% w/v

Question 11

What is the most common stationary phase?

Answer 11

Silica gel

Question 12

Name two other polar stationary phases?

Answer 12

Cellulose and alumina

Question 13

What do more polar compound absorb more onto?

Answer 13

The stationary phase and less time in the mobile phase

Question 14

What is the Rf usually quoted as?

Answer 14

Rfx100 value

Question 15

What is the intensity of a spot on a TLC plate related logarithmically to?

Answer 15

The concentration of the analyte producing it

Question 16

As polarity increases what happens to the Rf value for each compound in the mixture?

Answer 16

The Rf value increases

Question 17

How is the sample visualised after separation?

Answer 17

Use if UV light is a non-destructive method

Need to use silica gel plate impregenated with fluorescent material

Question 18

What wavelength does the sample illuminate at?

Answer 18

254 nm

Question 19

Name a general purpose developing reagent?

Answer 19

Iodine spray

Question 20

What does iodine produce?

Answer 20

Brown spots with many organic compounds

Question 21

What is potassium permanganate used for?

Answer 21

Detection of sugars and sugar- like molecules

Question 22

What is Ninhydrin solution used for?

Answer 22

Detection of primary and tertiary amines.
Used in the identification of aminoglycoside antibiotics such as gentamycin.
Also used in conjunction with Dragendorff reagent

Question 23

What % is ethanol/sulfuric acid used in producing fluorescent spots from corticosteroids?

Answer 23

20%

Question 24

What are applications of TLC?

Answer 24

Limit tests- example such as impurities in hydrocortisone acetate

Question 25

What are strengths of TLC?

Answer 25

Flexible: mobile and stationary phase, spray reagents.
Robust and cheap
Entire chromatogram can be seen
Used for many drugs impurities
Can be run in batches and can be automated

Question 26

What are limitations of TLC?

Answer 26

Limited number of theoretical plates available for separation
Limited sensitivity
Unsuitable for volatile compounds
Requires a degree of operator skill

Question 27

What is chromatography?

Answer 27

Is one of the best methods for separating and measuring the components of a mixture