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Applied science unit 2c :chromatography
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Chemistry reportWhat is chromatography
Chromatography is a method to physically analyse, identify, purify and quantifying an unknown
mixture into individual component. It is a typical lab experiment used to find out the unknown
component in mixture. Mikhail tsweet in 1901, during his research on plat pigmentation, invented
chromatography and was able to separate the numerous plat pigment.
What is adsorption
It is when atoms or molecules from liquid, melted solid or gas produce a thin membrane of
adsorbate to stick or adhere to the surface of the absorbent. The process is completely different
from absorption where the fluid is drawn into the solid
What is basic scheme for separation
Based on their adsorbate affinity, each compound within a mixture of mobile phase are differentiate
in the stationary phase. This is because each of components in a mixture have different polarities, so
when it passes though the stationary phase, one will migrate faster than the other. The component
that adsorb the most in the stationary phase tends to more slowly compared to others. Within the
stationary phase, each components of mixture will be spilt into discrete band because molecules of
the component will move in groups.
Principle of separation of different component
There are two important principle of separation
the higher the affinity the slower the molecules will move
the lower their affinity the faster the molecules will
the affinity refers to the how adsorbate the mobile phase is. Because of their different affinity the
samples can be separated into their different component. Another factor to consider is that the
bigger the molecule the slower it will travel compared to smaller ones as it travels quickly.
what is mobile phase?
The mobile phase is a substance which can be liquid or gas that that carry the components of the
mixture is forced though a stationary phase, which can be solid or semi- solid. It carries the sample
so that it mobile. The most common type of mobile phase is liquid chromatography
What is stationary phase
Stationary phase is any type of absorbent material that is effective at separating component of
mixtures. It does not react to the with the mobile phase or the mixture. It is often a porous solid,
typically glass, aluminium or silica that are placed fixed inside the column. There are two types of
stationary phase which are liquid stationary and solid stationary. The are only two types of solid
stationary which are
paper chromatography: the stationary phase is the paper
thin layer chromatography (TLC): the stationary phase is the
,what is paper chromatography
paper chromatography, in analytical chemistry, is a chromatography technique that uses an
absorbent paper as a stationary phase through which a solution typically the mobile phase passes
through it. It is used to separate chemical compound by showing the differing rating of
transportation in each compound. This is the most basic type of chromatography
how does paper chromatography work?
it works when a gas or fluid is forced through an adsorbent paper. As they are forced through the
material, the molecules are prone to scattering due to their different rate of speed which cause the
resulting colour band in the paper. The end result of the experiment is determined by the method
used to do the chromatography.
Factors affecting paper chromatography
the type of paper use: the type of paper used can play a significant affect on the result of
the experiment as some types of paper are suited fror chromatogram with their absorbing
and retaining nature while other makes it extremely difficult for the mobile phase to pass
through
type of mobile phase used: the different types of mobile phases have different levels of
solubility which could produce a different effect on the result of the chromatography
the viscosity of the paper: the ability of the mobile phase to travel upwards if affect by the
viscosity of the paper as thicker paper will have a harder time moving upward compared to
thinner ones
difference in temperature: the temperature of the room or environment can affect the
result of the experiment because the mobile phase might evaporate in a hotter
environment due to their solubility compared to colder ones
concentration of the solution: it the concertation of the mixture to be identified is very
weak it will be very difficult to see the see the result correctly
Advantages disadvantages
The separating procedure is completed is a Complex mixture can’t be separated as they are
short amount of time not efficient and often errors in results
The method for setting up is easy to understand Compared to TLC, paper chromatography isn’t
and quick very effective
It is quick and easy compared to other It can’t be kept for a long period of time as the
techniques results tend to fade away
, Paper chromatography of chlorophyll
Equipment’s
Filter paper/ chromatography paper
Leaf sample
Pestle and mortar
Gloves
Safety goggles
Toothpick
ruler
pencil
small capillary tube
sand
chemical: propanone; it is highly flammable and is a irritant
heathy and safety
wear gloves, safety googles and lab coat when doing the experiment
remove all bags and coat away from the experiment site
broken glass must be placed cautiously in the yellow bin
any accident or spills must be told to the teacher. Rinse skin immediately if it comes in
contact with chemical
stationary phase: paper
mobile phase: usually water
it is a basic technique used in chromatography
Method
I Fill the mortar with the sample leases to a depth of around 2cm. using a pipette add around 6 drops
of propanone and a small quantity of sand then grind until made into pigment (if the pigment is dry
you can add some more propane). I drew a line 3cm from the bottom on the strip of
chromatography paper using s pencil. Using a fine glass tube, I extract the liquid from the pigment
and place it in the middle of the line. Once the spot is dry add, I another drop of the liquid extract
and repeat it 5 times, making sure to allow each drop to dry before putting the next drop. I fill a
beaker with around 10cm3 of propanone making sure the propanone level is less than line. Once the
chromatography begins, do not move the beaker until the propanone has soaked to the top of the
paper then remove from the beaker. Once the chromatography dried, I marked how high the
propanone was on the paper with a pencil
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