Types of Chromatography

Question 1

what is chromatography?

Answer 1

• used to separate individual components from a mixture of substances

Question 2

what are the phases in chromatography?

Answer 2

• stationary phase
• mobile phase

Question 3

what is the stationary phase?

Answer 3

phase that does not move, it is normally a solid and liquid

Question 4

what is a mobile phase?

Answer 4

phase that does move, it is normally a liquid or gas

Question 5

what does TLC do?

Answer 5

• TLC indicates how many components are in a mixture

Question 6

what does TLC use?

Answer 6

• uses TLC plate

Question 7

what is a TLC plate?

Answer 7

• usually a plastic/metal sheet or glass
• coated with a thin layer of a solid absorbent substance
• usually silica

Question 8

what is the adsorbent in TLC?

Answer 8

• the adsorbent is the stationary phase in TLC

Question 9

how do we measure the Rf value?

Answer 9

• distance moved by the solute divided by the distance moved by the solvent

Question 10

why can the results of a TLC not be seen to the naked eye?

Answer 10

• the solutes are colourless, so a UV lamp may be used

Question 11

why do different components move along the chromatography paper?

Answer 11

• different molecules in a mixture would have different affinities for the mobile an stationary phase so will move at different rates within the mobile phase

Question 12

what is the stationary phase is gas chromatography?

Answer 12

• high boiling liquid which is adsorbed onto inert solid support

Question 13

what is the mobile phase in gas chromotography?

Answer 13

• inert carrier gas
• e.g. helium or neon

Question 14

what is the process of gas chromatography?

Answer 14

• small amount of volatile mixture injected into the apparatus
• mobile carrier gas carries components in sample through capillary column
• components slow down when they interact with the liquid stationary phase inside the column

Question 15

what happens in gas chromatography is the component is soluble?

Answer 15

• more soluble component in liquid stationary phase the more it moves through capillary column

Question 16

what happens after components move through the capillary column?

Answer 16

• components reach the detector at different times are they are retained in column
• those retained in column shortest time has lower retention time = more soluble

Question 17

how can gas chromatograms be interpreted?

Answer 17

• retention times
• peak intergetation

Question 18

what are retention times?

Answer 18

• how many components are in the mixture
• size of peaks is the proportion in the mixture

Question 19

what are peak intergretaion?

Answer 19

• area under the peak
• allows us to find the concentrations of components in sample