chromotography and instrumentation in organic chemistry

Question 1

what is chromatography

Answer 1

chromatography is a separation technique in which a mobile phase carrying a mixture moves in contact with a selectively absorbent stationary phase

Question 2

what is the principle upon which all chromatographic separation techniques are based

Answer 2

the principle on which all chromatographic separation techniques are base is that separation of components occurs as a result of selective absorbance of the components onto a stationary phase when carried by a mobile phase

Question 3

what is 
a) the mobile phase
b) the stationary phase
c)solid inert particles spread on column
in gas chromatography

Answer 3

a) unreactive gas eg nitrogen
b) non volatile liquid eg long chain alkanes
c) silica or alumina

Question 4

what is the principle of gas chromatography

Answer 4

that a gaseous mobile phase is in contact with a stationary phase and the separation of the mixture occurs as a result of selective absorbance of the components of the mixture on the stationary phase

Question 5

what is the principle of high performance liquid chromatography

Answer 5

that a liquid mobile phase is in contact with a stationary phase and separation of the mixture occurs as a result of selective absorbance of the components of the mixture on the stationary phase

Question 6

what are the four processes of gas chromatography

Answer 6

1) injection
2) vaporisation and carrying through tube by inert gas (carrier gas) through hot column
3) detector records signal and plots gas chromatogram

Question 7

use of gc

Answer 7

measure levels of blood or alcohol in urine samples

Question 8

what does hplc stand for

Answer 8

high performance liquid chromatography

Question 9

summarise the processes involved in HPLC

Answer 9

• injection of sample
• pumping of sample
• separation of sample in column
• detection of components
• display of results

Question 10

uses of hplc

Answer 10

analysis of food

measure concentration of caffeine in energy drinks

Question 11

what is the principle of infra-red spectrometry

Answer 11

that organic compounds absorb infra-red radiation of certain frequencies. the combinations of frequencies that are absorbed depend on the bonding within the molecuke and are unique to the particular molecule

Question 12

outline main processes involved in infra red spectrometry

Answer 12

• ir radiation passed through sample
• IR radiation of certain frequencies is absorbed
• absorption spectrum is obtained

Question 13

uses of IR spectrometry

Answer 13

identifying plastics and illegal drugs

Question 14

what is the principle of ultra violet spectrometry

Answer 14

absorbance is directly proportional to the concentration of the substance

Question 15

outline the processes involved in ultraviolet spectrometry

Answer 15

solution of substance being analysed is placed between a source of UV light and a detector
detector measures the intensity of light reaching it
uv absorption spectrum is obtained