6.3 Analysis Flashcards
(31 cards)
What is the main use of chromatography
To separate a mixture of optical isomers
What is a stationary phase
Made out of silica
It stays still, and the solvent will travel through it
What is the mobile phase
Solvent
It moves mixture with a mix of affinities
How do mixtures travel up the chromatography paper
components will have strong interactions with the stationary phase, and the mobile phase will drag it through
Describe thin layer chromatography’s mobile and stationary phase
The stationary phase is solid
The mobile phase is liquid
How to carry out TLC
- Draw a 1cm pencil line
- Use a capillary tube and dab a small dot of the mixture on the pencil start line
- Place in a beaker with the solvent below the pencil start line
- Place a lid on the beaker, and leave it
- After it is done mark the solvent line quickly as the solvent will evaporate once the lid is removed
For TLC the stronger the affinity (interactions) between a pigment and start line the slower it will travel
TRUE OR FALSE
TRUE
Use of Thin layer chromatography
To check how many components you have
And very quickly and effectively identify components/pigments
Describe the mobile and stationary phase is gas chromatography
The stationary phase is a liquid
The mobile phase is an inert gas, such as helium or nitrogen
Describe how to carry out gas chromatography
- Inject sample directly into a column which contains a liquid stationary phase
- Blast helium through the column which will act as the mobile phase
- If components are not soluble it will remain a gas and be pushed u more quickly (less retention time)
How does gas chromatography separate components
By solubility to the stationary phase
How does thin layer chromatography separate components
By different affinities to the stationary phase
How will an increase is temperature affect retention time
Decreases retention time
How does a decrease in boiling point affect retention time
Will decrease retention time
What does the area under peaks after chromatography represent
The concentration of that component if you have a reference
How to carry out a calibration curve
- Prepare a standard solution for every component
- Run through gas chromatography
- Run each standard solution from a machine
- Plot a calibration curve with the values/data collected
What is NMR
A very powerful technique to examine molecular structure in detail
Only works with odd numbered isotopes
Interested in either carbons or protons
Describe how NMR works
- Blasts radio waves into the dissolved sample, which causes the nucleus to absorb the radio waves and enter resonance
- We then measure the frequency of the radio waves by computer which is measured in chemical shifts
What does it mean if a nucleus enters resonance
It flips between being excited and relaxed
What is a standard reference chemical used in NMR
We use TMS which will always have a chemical shift at zero
What solvent do we use in NMR and why
CDCl3 as it doesn’t react, so it will not affect the spectrum
What do the number of peaks on NMR represent
The number of chemically different carbons in a compound
What does the value of the chemical shifts tell us
The different chemical environments of the carbon
What happens if we have two identical carbons
Their peaks will directly overlap and will become taller
