Chromatography

Question 1

What is chromatography?

Answer 1

is a technique used to separate and identify components in a mixture.

Question 2

What are some of the types of chromatography?

Answer 2

1)TLC (Thin Layer Chromatography)
2)Gas chromatography
3)Paper chromatography
4)Column chromatography

Question 3

What are the 2 phases that are required for separation in chromatography and what is it?

Answer 3

stationary phase-the phase that the compound travel across that does not move,must be solid or liquid on a solid support.

Mobile phase-is a carrier for compounds through the stationary phase,is either liquid or gas.

Question 4

What are some of the basic principles all types of chromatography use?

Answer 4

-The mobile phase moves over or through the stationary phase.

-The solubility of the substance in the mobile phase and its retention by the stationary phase determines the distance the substance moves up the plate.

-The more the substance is soluble in the mobile phase the further up the plate it will travel.

Question 5

What is the mobile and stationary phase in paper chromatography?

Answer 5

stationary phase-paper
mobile phase-water

Question 6

How is TLC (Thin Layer Chromatography) carried out?

Answer 6

-A plate is coated with a solid and a solvent moves up the plate.
-Stationary Phase-Absorbent material such as silica(silicon dioxide) or aluminium oxide on a glass or metal plate.
-Mobile phase-solvent(can be altered depending on the compound)
-The purity of a sample can be determined-sample is impure if more than one dot appears.

Question 7

How would we be able to see the colorless dots?

Answer 7

-Both coloured and colourless chemicals can be separated by TLC.
-Colourless chemicals will not be seen.
A way of making the colourless dots visible:
-UV Light
-Iodine vapour

UV Light-TLC plate contains fluorescent dye,under a UV light the spots where the chemicals are will up as dark patches.
-Iodine vapour-The TLC plate is placed in a sealed jar with iodine crystals.
>Iodine vapour sticks to the chemicals on the plate.
>Spots turn brown/purple

Question 8

What is Gas chromatography?

Answer 8

Is an analytical method used to determine volatile components and their amounts in a mixture.

Question 9

What is the stationary and mobile phase in gas chromatography?

Answer 9

mobile phase-inert carrier gas(helium)
stationary phase-packed column

Question 10

How does gas chromatography work?

Answer 10

1)Volatile mixture is injected into the GC.

2)Mixture is vaporized due to the heat of the oven.

3)Carrier gas pushes the sample through the column.

4)The detector records the time taken for a substance to go through the column which is sent to the computer.

5)A graph is plotted showing the time each components reached the detector.

Question 11

What are the applications in chromatography?

Answer 11

-Forensics-analysing blood or fibre samples
-Drug testing-test a person’s breath to see if they have consumed any alcohol or drugs.
-pharmaceutical industry -test the purity
-Separating enantiomers

Question 12

What is column chromatography?

Answer 12

is a technique which is used to separate a single chemical compound from a mixture dissolved in a fluid.

Question 13

What are the names of 2 gas chromatography detectors?

Answer 13

1)Flame ionization detector
2)Thermal conductivity detector

Question 14

What is Flame ionization detector (FID)?

Answer 14

As the sample exits the column,it is burned in a hydrogen/air flame and ionized particles are measured as an electrical current.

Question 15

What is Thermal conductivity detector?

Answer 15

Thermal conductivity detectors are the most widely used detectors in gas chromatography. These detectors use heated metal filament (or thermistors that are made of some semiconductor of fused metal oxides) to sense small changes in thermal conductivity of the carrier gas.

Question 16

How do you work out the retention factor?

Answer 16

DIstance travelled by the centre of a spot to the distance travelled by the solvent front.

Question 17

What is retention time?

Answer 17

time taken for a component of a mixture to travel through the column.Retention time is unique so can be used to identify components.

Question 18

What is mass spectrometry?

Answer 18

Mass spectrometry is an analytical tool useful for measuring the mass-to-charge ratio (m/z) of one or more molecules present in a sample.

Question 19

What are 4 things that happen when a sample is squirted into a time of flight mass spectrometer?

Answer 19

1)Ionisation
2)Acceleration
3)Ion drift
4)Detection

Question 20

Explain each phase that takes place in mass spectrometry?

Answer 20

1)Ionization-Two ways of ionizing your sample are:
Electrospray ionization-the sample is dissolved and pushed through a small nozzle at high pressure.A high voltage is applied to it,causing each particle to gain an H+ ion.The sample is turned into a gas made up of positive ions.

Electron impact ionization-the sample is vaporized and an ‘electron gun’ is used to fire high energy electrons at it.This knocks one electron off each particle,so they become +1 ions.

2)Acceleration-the positively charged ions are accelerated by an electric field so that they all have the same kinetic energy.(This means that the lighter ions will end up moving faster than the heavier ions).

3)Ion drift-the ions enter a region with no electric field,so they just drift through it.Lighter ions will drift through faster than heavier ones.

4)Detection-Because lighter ions travel at higher speeds in the drift region,they reach the detector in less time than heavier ions.The detector detects charged particles and a mass spectrum is produced.

Question 21

What is high performance liquid chromatography?

Answer 21

Is a type of column chromatography that uses very small particles and high pressures to achieve better separation.

Question 22

What are some of the advantages of HPLC(high performance liquid chromatography)?

Answer 22

-greater speed
-higher resolution(ability to separate two very similar subastances).
-can also be scaled up to operate as a purification method on a much larger scale, handling grams or even kilograms of substance.