This is an in depth assignment discussing how to correctly use
chromatographic techniques to produce chromatograms, the use of
chromatographic techniques to separate mixtures, and analyse own
chromatograms and relate the factors that affect the separation of mixtures to the quality of result...
Zoe Bella Hollingsworth
Pearson level 3 BETC national diploma in forensic and criminal investigation
Unit 2c assignment 3
Introduction
Mixtures usually contain two or more substances, which are physically mixed
but not chemically combined. Mixtures can be separated by many methods,
for example chromatography. There are two different types of
chromatography, planar (paper chromatography or thin-layer
chromatography) and column (liquid chromatography, high performance
liquid chromatography, gas chromatography, or ion exchange
chromatography). Chromatography is used to separate mixtures, so that
each component in the mixture can be identified. It does this by separating
components based on their interaction with the mobile and stationary phase.
In the mobile phase if the component is more soluble, then it will move
faster. In the stationary phase if the component binds more strongly to this
phase, it will move slower.
Part 1 (paper chromatography of ink)
Paper chromatography can be used to identify and analyze chemicals in
mixtures, it works because some compounds can dissolve more in a solvent
than others can, so when the solvent moves along a sheet of
chromatography paper, the different substances will move at different speeds
along the sheet, forming the mobile and stationary phase.
Advantages and disadvantages of paper chromatography
Advantages
It can separate water soluble compounds (e.g., ink).
The dyes can be detected by the naked eye.
Disadvantages
A limited type of mobile phases can be used.
The chromatography paper can be prone to ‘smearing.’
Risk assessment
Risk Prevention of risk
Beaker (if smashed it could cut Make sure to be careful when
someone). handling glass and clean up any
broken glass.
Capillary tube (if handled incorrectly Handle the tube carefully.
it could be broken).
Method= to start with we set up a beaker with 3cm (about 1.18 in) of water
inside it, then cut a piece of filter paper into a small strip. Then we drew a
, pencil line 1cm (about 0.39 in) up from the bottom of the filter paper, we
used a pencil instead of a pen to draw the line because pencil would not
affect the chromogram unlike the pen which would interact with the water in
the beaker and affect the results. Then we added two dots of colored ink onto
the pencil line, then we put the filter paper into the beaker, making sure the
water did not go over the pencil line because if it did there would not be a
result to use to calculate a Rf value, we attached the filter paper to a pencil
and rested it on top of the beaker. We took the filter paper out of the beaker
when the solution had reached 1cm (about 0.39 in) from the top and allowed
the paper to dry and calculated the Rf value.
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