Chromatography Flashcards
Types
Paper Chromatography
Thin-Layer Chromo TLC
Gas Chromo GC
High-performance Liquid chromo HPLC.
Each type has a mobile and stationary phase.
PC
The basic form of chromo used for qualitative analysis of mixtures especially inks and food colouring. The stationary phase of absorbent paper. The mobile phase of solvents in which components are dissolved.
Separation occurs due to varying solubilities of components in the solvent and water in paper fibres.
TLC
Used for separating and analysing molecular mixtures faster and better separation than PC. TLC plate consists of a thin layer of absorbent material.
Stationary phase = absorbent material.
Mobile Phase = The solvent.
The solvent moves up the plate through capillary action carrying the components with it.
Components absorb and desorb at different rates due to chemical structure and ability to form intermolecular bases to the stationary and mobile phases.
Rf is characteristic for each sample under the same condition, plant pigments and drugs.
GC
The carrier gas is the mobile phase. The sample is injected into the oven, gas moves vaporised particles through fine long columns of stationary, smallest solutes that absorb the least dilute first.
Rf depends on temperature, length of column, flow rate and chemical structure. Indicates what the sample is, under peak indicates the amount of substance present. Standards are used to confirm identity and prepare a calibration curve for the calculation of amounts.
HPLC
Similar to GC but the mobile phase is a liquid unlike the gas in GC liquid plays an important role in absorption and desorption. Needs a pump to push the liquid into the denser-packed column.
Rf indicates what sample is, very simple to GC refer to above rates.
Retardation Factor
A measure of how mobile a component is in a mixture.
Rf = Distance travelled by component/distance travelled by solvent.
Rf cannot be greater than 1.
Moles, concentration formulas
n = m/mm
C1V1=C2V2
C= n/v
