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BTEC APPLIED SCIENCE UNIT 19 - Learning aim C
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C: Investigate chromatographic techniques to identify components and determine the amounts present in samples. Grade Distinction.
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Emilia HawkinsUnit 19: Practical Chemical Analysis
C: Investigate chromatographic techniques to identify components and determine the amounts
present in samples.
High performance liquid chromatography (HPLC)
High performance liquid chromatography is a technique used to separate, identify and quantify
different components in a mixture. The HPLC column is made up of a variety of components which
are all essential for accurately separating a mixture. It consists of a solvent delivery pump, a
degassing unit, sample injector, a column oven, a detector and a data processor. The stationary phase
in HPLC is silica, which is a polar substance and the mobile phase in HPLC is a mixture of components
with a low polarity, which can be adjusted to allow for the best separation. In reverse phase HPLC,
the stationary phase is non-polar hydrocarbon chains attached to silica and the mobile phase is a
more polar substance. High performance liquid chromatography is used in pharmaceutical
development to test for the purity of products and in medical diagnoses in testing for vitamin D
deficiency. High performance liquid chromatography is a reliable way to test for the purity of
products in the pharmaceutical industry. HPLC separates the different components of a mixture and
allows scientists to test if a sample of a compound is pure as contaminants would be highlighted in
the chromatograph. It is reliable because the entire process is done using a machine where there is
little possibility for human error. This also makes results reproduceable and valid.
https://theory.labster.com/niche_hplc/
Gas chromatography
, Emilia Hawkins
Gas chromatography is also used to separate components in mixture but instead uses a gas to
transport the unknown mixture through the stationary phase. A gas chromatograph is made up of an
injection port, a column, carrier gas control equipment, ovens and heaters for maintaining
temperatures of the injection port and the column, an integrator chart recorder and detector. In gas
chromatography the stationary phase is a microscopic layer of liquid which is on the surface of solid
particles in a column, and the mobile phase is an inert carrier gas. Gas chromatography is most
commonly used to
identify volatile
flammable
substances in
forensic fire
analysis, to identify
fibres in forensics
and to identify
organic
environmental pollutants. Gas chromatography can be used in a real life setting by monitoring
pollution in the air. This is able to give researchers a better insight into where air pollution is most
prominent and how it changes over a period of time. It can also be used to identify volatile organic
compounds which are released into the air by products such as cleaning solutions and paint for
textiles. Gas chromatography is able to separate the chemicals found in these products from the air
and provide information on how impactful they are.
https://www.researchgate.net/figure/Schematic-diagram-of-the-main-components-of-a-gas-
chromatography-system-Philadelphia_fig3_273134301
Gas chromatography for fire analysis
1. Measure the peak height and retention time of the seven n-alkane. These are the most
intense peaks which have been numbered for you. Use a ruler to measure the peak height, in
mm, and read the retention time from the x-axis. Record the data in Table 1.
Table 1. Data table for GC of paraffin
Peak id Carbon no. Retention time (min) Peak height (mm)
1 C9 7 39
2 C10 8.75 51
3 C11 10.25 53
4 C12 12.25 43
5 C13 13.75 37
6 C14 15.25 33
8 C15 16.5 10
2. Identify the seven peaks in the n-alkane series from the retention times you recorded in
Table 1, and record their peak heights and retention times, in Table 2.
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