Chromatography and functional group analysis
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what are the phases in chromotography?
stationary and mobile phase
describe the stationary phase
does not move and is usually a solid or a liquid supported on a solid. Area in which material seperates
describe the mobile phase
does move and is normally a liquid or a gas. It moves materials, seperating them over the stationary phase.
what can chromatography be used for?
the analysis of drugs, plastic, flavourings, air sample and applications in forensic science.
what is thin layer chromatography?
a quick and inexpensive analytical technique that indicates how many components are in a mixture. The technique usually uses a TLC plate (plastic sheet or glass) coated with solid adsorbent substance- silica.
what is the stationary phase in TLC?
adsorbent
what is adsorption?
process by which silica holds different substances in the mixture to its surface
how is separation achieved in TLC?
by relative adsorptions of substances with stationary phase. Different components in mixture have different affinities for the absorbent.
how do you carry out TLC?
-draw a base line using a pencil about 1cm from the plate end -spot sample on base line using a capillary tube -pour solvent into beaker at depth of 0.5cm and place watch glass on top -place TLC plate in beaker with watch glass on top. -allow solvent to rise until 1cm below top of plate -remove plate and immediately mark solvent front with pencil -circle the invisible and visible spots
how do you calculate Rf value?
distance moved by component/ distance moved by solvent front
what is gas chromatography used for?
it is useful for separating and identifying volatile organic compounds present in a mixture
what is the stationary phase in gas chromatography?
high boiling liquid adsorbed into inert solid support
what is the mobile phase in gas chromotography?
inert carrier gas such as helium or neon
how does gas chromatography work?
-small amount of volatile mixture is injected into gas chromatograph. -The mobile carrier gas carries the components in the sample through the capillary column which contains liquid stationary phase absorbed onto the solid support -the components slow down as they interact with the liquid stationary phase.
how are the components in a mixture separated in gas chromotography?
depending on solubility in the liquid stationary phase. The more soluble, the slower it moves through the capillary column.
how are compound in a mixture detected in gas chromotography?
components in a mixture reach the detector at different times depending on solubility.
what is retention time?
the time taken for each components to travel through the column
what two pieces of information can be obtained from a gas chromatogram?
-retention time -peak integrations
what is paper made of?
cellulose
what is the mobile phase in paper chromatography?
solvent
what is the stationary phase in paper chromatography?
water molecules
how are components separated in paper chromatography?
dependent on relative solubility. If the sample is more soluble in the mobile phase, it moves up. If more soluble in the stationary phase, it will stay towards the bottom
how do you identify compounds using chromatography?
by comparing Rf values to a database
how can you detect invisible solutes?
-use UV light -spray with ninhydrin. When sprayed, the spots will turn purple.