Chromatography

Question 1

Chromatography

Answer 1

Method of separating mixtures of soluble substances

Question 2

Stationary phase

Answer 2

Can be solid or a liquid

What the components of the mixture move through

Distance depends on strength adsorption

Question 3

Mobile Phase

Answer 3

Most often liquid or gas

Components of mixture dissolve

Components separated bc they move at different rates as mobile phase moves

Question 4

Types of Chromatography

Answer 4

Paper - water bonded to cellulose in paper is stationary phase and solvent is mobile phase

Thin-Layer - silica in silica gel is stationary phase, solvent is mobile phase

Question 5

Running A Chromatogram

Answer 5

•Prepare a conc solution of the mixture

•Mark origin line in pencil near bottom of paper/TLC plate and put x in middle

•Apply conc solution to centre of X using capillary tube - allow solvent to evaporate

•Place paper/TLC in solvent and run until solvent close to top

•mark position of solvent front with pencil - allow chromatography to dry

•develop using a chemical development agent or UV light

Question 6

Analysis of Chromatogram

Answer 6

•Mark position centre each spot
•Measure distance of centre spot from origin
•measure distance solvent front from origin
•calculate Rf value for each spot

Question 7

Rf Value

Answer 7

Rf= distance moved by spot/
distance moved by solvent

Question 8

Two Way Paper Chromatography Method

Answer 8

•prepare conc solution of mixture

•mark origin line with pencil mear bottom and another at 90° to first line

•apply conc solution of sample at intersection of 2 lines - allow solvent to evaporate

•place in storable solvent & run until solvent is close to top of paper - mark front and allow dry

•Rotate chromatogram 90° and run different solvent as before - allow to dry

•Develop using development agent/UV light

Question 9

Suitable Solvents for Two Way

Answer 9

Ethanol
Propanone

Question 10

Analysis Two Way

Answer 10

•mark position centre each spot
•measure distance of centre spot from origin
•measure distance solvent front from origin
•calculate Rf for each spot
•Repeat for second solvent and determine second Rf values

Question 11

Benefits Two Way

Answer 11

Allows more definite separation of a complex mixture

Question 12

Gas-Liquid Chromatography Mobile and Stationary

Answer 12

Mobile Phase: inert carrier gas (Noble or Nitrogen)

Stationary Phase: oil or liquid held on solid support

Question 13

Gas-Liquid Chromatography

Answer 13

Gaseous sample mixed with gas and passed through a coiled tube (column) in an oven

Components partition themselves between inert gas phase and liquid stationary phase

More soluble = longer they will stay in coiled column

As separate - components come out of column at separate times

Question 14

Area under and above peak GLC

Answer 14

Under peak of detector signal gives measure of relative concentration of that component

Above peak gives measure of area under the curve

Question 15

Relative Concentration GLC

Answer 15

Calculated by dividing area under particular peak by total of areas for all peaks

Question 16

Retention Time

Answer 16

time taken from injection until a component reaches the detector