Taha Ismaeel
19080333
Chemistry
Separate to Identify
Unit 2: Practical Scientific Procedures and Techniques
C: Undertake chromatographic techniques to identify components in mixtures.
What is chromatography and what is it used for:
Chromatography is a physical process for separating components of a mixture. This is done
to analyse, purify the different substances for further investigation, identifying the
components found in the mixture or to quantify mixtures or components to see how much
of each component there is in the mixtures. This technique is used to analyse to examine
mixtures and different components, different solvents, usually during criminal investigations
or investigating the different solvents in a mixture. This is also used when analysing a
person's blood to detect alcohol levels.
This is a physical procedure as mixtures are not chemically combined. To get the process
started, the mixture is dissolved in a substance called the mobile phase, which carries it
through a second substance called the stationary phase. The principle of ‘partition’ affinity
between 2 phases of a mixture. A component with a higher affinity will travel furthest
during mobile phase.
Stationary Phase: A layer on the supporting the product that is reacting with the analytes.
Mobile Phase: mobile phase is the solvent that moves through the paper, carrying different
substances with it.
Supporting medium: A solid area which where the stationary phase is bounded.
The different components in the mixture travels in the stationary phase at different speeds,
subsequently causes the different solvents to separate. The stationary and mobile phases
determine which substances move fast and which ones moves slower. And this is how the
solvents sperate. This is called retention time. This technique is used to analyse different
solvents, usually during criminal investigations or investigating the different solvents in a
mixture.
, Taha Ismaeel
19080333
Chemistry
What factors affect separation:
factors Factors affecting separation
Paper chromatography -Length of the chromatography paper. Having a longer paper will
be better as the solvents can spread as much as they need.
having a short paper may not allow the solvents to all show up as
some may spread at different speeds compared to others.
-Thickness of the paper. The thicker the paper he more difficult
the solvent and mixture to travel upwards and to go into the
mobile phase.
-Quality of the paper used. Different chromatography papers
retain and absorb better compared to others. Experimenting
with different types of paper will help to identify the best one.
-Type of solvent used. compounds have different solubility
compared to other compounds. Thus, different separations could
occur when using different solvents.
-Effect of temperature. The higher the temperature, the faster
the exchange of the analytes between the mobile phase and the
stationary phase.
-Concentration of the sample/spot. Enough of the mixture needs to be
added. If enough isn't added it will not separate enough and will not
be able to see. If you put too much it will not sperate correctly.
RF Value -Temperature
-Quality of paper
-Solvent used
-Distance which the solvent travelled
-Thickness of layer for TLC
-How the sample was placed
-Nature of absorbent
Chromatography How well the mobile phase was done, stationary phase.
technique The flow rate of the solvents.
Concentration of the analyte
How porous the paper is during the stationary phase.
The surface area of the stationary phase
Differences between paper and TLC and when are these used.
19080333
Chemistry
Separate to Identify
Unit 2: Practical Scientific Procedures and Techniques
C: Undertake chromatographic techniques to identify components in mixtures.
What is chromatography and what is it used for:
Chromatography is a physical process for separating components of a mixture. This is done
to analyse, purify the different substances for further investigation, identifying the
components found in the mixture or to quantify mixtures or components to see how much
of each component there is in the mixtures. This technique is used to analyse to examine
mixtures and different components, different solvents, usually during criminal investigations
or investigating the different solvents in a mixture. This is also used when analysing a
person's blood to detect alcohol levels.
This is a physical procedure as mixtures are not chemically combined. To get the process
started, the mixture is dissolved in a substance called the mobile phase, which carries it
through a second substance called the stationary phase. The principle of ‘partition’ affinity
between 2 phases of a mixture. A component with a higher affinity will travel furthest
during mobile phase.
Stationary Phase: A layer on the supporting the product that is reacting with the analytes.
Mobile Phase: mobile phase is the solvent that moves through the paper, carrying different
substances with it.
Supporting medium: A solid area which where the stationary phase is bounded.
The different components in the mixture travels in the stationary phase at different speeds,
subsequently causes the different solvents to separate. The stationary and mobile phases
determine which substances move fast and which ones moves slower. And this is how the
solvents sperate. This is called retention time. This technique is used to analyse different
solvents, usually during criminal investigations or investigating the different solvents in a
mixture.
, Taha Ismaeel
19080333
Chemistry
What factors affect separation:
factors Factors affecting separation
Paper chromatography -Length of the chromatography paper. Having a longer paper will
be better as the solvents can spread as much as they need.
having a short paper may not allow the solvents to all show up as
some may spread at different speeds compared to others.
-Thickness of the paper. The thicker the paper he more difficult
the solvent and mixture to travel upwards and to go into the
mobile phase.
-Quality of the paper used. Different chromatography papers
retain and absorb better compared to others. Experimenting
with different types of paper will help to identify the best one.
-Type of solvent used. compounds have different solubility
compared to other compounds. Thus, different separations could
occur when using different solvents.
-Effect of temperature. The higher the temperature, the faster
the exchange of the analytes between the mobile phase and the
stationary phase.
-Concentration of the sample/spot. Enough of the mixture needs to be
added. If enough isn't added it will not separate enough and will not
be able to see. If you put too much it will not sperate correctly.
RF Value -Temperature
-Quality of paper
-Solvent used
-Distance which the solvent travelled
-Thickness of layer for TLC
-How the sample was placed
-Nature of absorbent
Chromatography How well the mobile phase was done, stationary phase.
technique The flow rate of the solvents.
Concentration of the analyte
How porous the paper is during the stationary phase.
The surface area of the stationary phase
Differences between paper and TLC and when are these used.
