(TLC) and
(TLC) and
(TLC) and
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is a stream of an inert gas, such as nitrogen or argon. The sample under investigation is<br />
volatilized <strong>and</strong> the vapour swept through a column of the stationary phas phase e by the carrier gas.<br />
Partition of the sample between the stationary <strong>and</strong> moving phases will occur. However, for liquid<br />
chromatography, , the system is eluted with a moving liquid leading to separation of the<br />
components of a mixture by the partitioning of the these se components between the stationary <strong>and</strong><br />
moving liquid phases so that the components will move at differing rates through the column.<br />
Paper chromatography is analogous to thin layer chromatography except that in this case, the<br />
support material consists of a sheet of specially prepared paper, <strong>and</strong> the stationary phase is<br />
considered to be water adsorbed on the paper. Elution with a solvent, measurement of the RRf<br />
R<br />
value <strong>and</strong> preparative work is carried out in the same way as for thin layer chromatography.<br />
3) Ion-Exchange Exchange Chromatography<br />
The third type of chromatography, ion-exchange chromatography, , is of somewhat more limited<br />
application in the chemistry lab, but is widely used in biochemistry. Here, the solid support<br />
consists of a resin which can have either bas basic ic or acidic properties, <strong>and</strong> mixtures of acidic or<br />
basic substances can be separated using these resins by eluting with buffers of different pH's.<br />
Part A: Thin Layer Chromatography of Analgesic Drugs<br />
In this experiment, <strong>TLC</strong> will be used to examine the composition of various analgesic (pain<br />
relieving) drugs. The best known of these is aspirin, but several other chemically similar<br />
compounds are (or were) also used as analgesics. Among these are phenacetin, salicylamide <strong>and</strong><br />
acetaminophen. Caffeine is some sometimes times added to these formulations to overcome drowsiness. A<br />
few other compounds such as N-cinnamylephedrine<br />
cinnamylephedrine (cinnamedrine) <strong>and</strong> diphenylpyrilene are<br />
included for other therapeutic effects, such as antispasmodic or slight sedative action. In addition<br />
to the active ingredients, the tablets of these drugs contain starch, lactose, <strong>and</strong> other substances<br />
that act as binders <strong>and</strong> permit rapid solution, <strong>and</strong> sometimes also inorganic bases. The objective<br />
of this experiment is to identify an unknown drug tablet by a <strong>TLC</strong> comparison with st<strong>and</strong>ard<br />
compounds.
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