Chapter 29 Chromatrography Flashcards
How does TLC chromatography work
Basicslly there are 2 phases, stationary and mobile.
The mobile phase carries the sample through thr stationary phase and based on strentgh of interactions between mobile and stationary will determine where the spots end up.
What is thr adsorbent phase in tlc
Adsorbent means to absorb, whereas absorbent is the thing being absorbed. The adsorbent is thus the di,it’s on the plate, the stationary phase. Different components in the sample will have different affinities for the adsorbent and bind thus at different stages
How to briefly do TLC, more importantly what to do at end
Draw pencil line 1 cm up, place sample , put in solvent , make sure below line, cover with watch glass, don’t evaporate! Let it ride, take out, draw line, let it dry
Now to make spots visible, can leave with iodine or spray it to locate them, or uv light etc
What are the rf retention factor values
The ratio. Fro the solvent used of how far it moved /solvent, and this will be same for everything m so can thus identify
Otherwise just use sample you think it’s there next to and see by eye
How does gas chromatography work
(What is mobile and stationary phase)
(What happens to volatilise substance in, what is retention time)
The stationary phase is a liquid adsorbed onto a solid support inside the chronogram, and the mobile phase is just dome inert has like helium
The volatile mixture is injected and carried by the carrier gas, the mobile phase. Based on level of interaction between the sample and the mobile / stationary phase, will the sample take longer to leave the chromatogram
Here the more soluble, the longer it will stay inside . Thr time taken to leave is called retention time and this is the thing that can be used ti compare what molecules have what.
Quick what is gas chromatography used for
For identifying substances in volatile samples
What two pieces of information can you tell from a gas chromatograph?
1) the retention time = which identified the substance
2) the peak area (area under the peak) = which alllws you to find out it’s concentration
How to find out concentrations of s substance identified using a gas chromatograph
Say you find out it was ethanol, want to find out conc
1) use known concentrations of ethanol and run them through same conditions in the gas chromatograph.
2) plot the relative peak areas against concentrations to make a calibration curve
3) now find out the area of ethanol you had found earlier
4) use the calibration curve to estimate the concentration
What are ethnically test for these things
Alkenes
HALOALKANES
carbinyl
Aldehyde
Primary secondary alchol aldehyde
Cabrixykic acid
Phenol
1) bromine water is decolorusied
2) SILVER NITRATE AND ETHANOL, warm to 50°, will produce milk cream butter
3) 2 4 DNP = orange
4) tollens reagent = silver mirror and carbox formed if aldehyde
5) acidified potassium dichromate will oxise and go from orange to green
6) sodium fabricate will cause effervescence
