ANALYSIS

Definition:

An analytical technique that separates components in a mixture between a mobile phase and a stationary phase.

• The mobile phase may be a liquid or a gas.
• The stationary pahse may be a solid (TLC) or a liquid or solid on a solid support (GC).

A solid stationary phase separates by ADSORPTION.

A liquid stationary phase separates by RELATIVE SOLUBILITY.

Distance travelled by component/ distance travelled by solvent.

• always less than 1

The time taken for a component to pass from the injector to the detector.

Tells us:

• Different retention times - number of components
• Relative peak areas- the proportions of components in a mixture

boiling point

the higher the boiling point, the longer the retention time

solubility

high solubility means less time carried by the mobile phase, so a longer retention time.

• Similar retention times
• No retention time reference for unknown compounds
• Only substances that can be made volatile.

WHY?

• provides a far more powerful analytical tool than chromatography alone
• Gas chromatography separates the substances by relative solubility.
• Mass spectra can be compared to a database for a positive identification of a component.

USES

• Forensics
• environmental analysis
• airport security
• space probes

feasp

Involves

• interaction of materials
• with the low-energy radiowave region
• of the electromagnetic spectrum.

CNMR analyse to:

• different types of carbon present from shift values
• possible structures

HNMR analyse to:

• different types of proton environments present from shift value
• relative numbers of each proton available from relative peak areas/integration trace
• Number of non-equivalent hydrogens adjacent using spin-spin splitting patterns
• Possible structures!!
• D2O allows OH peaks to be identified

TMS

• A standard for chemical shift measurements

Deuteration

• solvents (C D Cl3) as they do not create peaks in the spectrum.
• Proton exchange using D2 O to replace O-H and N-H groups

USED IN 

• Magnetic Resonance imaging (MRI)
• to obtain diagnostic information about internal structures.
• in body scanners.

INFRARED

• to identify presence of functional groups

MASS SPECTRUM

• identify parts of structures
• using molecular ion peaks and fragmentation
• M/Z may not be there as is too unstable!

Molecular ion:

• The heaviest ion, the original molecule.
• SOMETIMES: there is no m/z peak as it is so energetically unstable it breaks down.

Base peak:

• The most abundant fragment

Infra-red spectroscopy

• key peaks (dont forget C-O)
• differences may be found in fingerprint region

Mass spectrum

• M/Z peak- same or different?
• key fragments