Chromatography Flashcards
Chromatography
Physical separation technique, Measures the rate at which components flow through the stationary phase
Stationary phase
What the mixture flows through
Mobile phase
Dissolves the components of the mixture
ADsorption
Where the components adhere/bond with the stationary phase
Desorption
When the components dissolve (bond with) into the mobile phase
Paper chromatography stationary phase
piece of paper placed in the solvent
Paper chromatography mobile phase
Solvent the paper is placed in
What is thin layer chromatography used for
Used to separate and analyse a wide variety of molecular mixtures
Thin layer chromatography
Uses a thin layer of silica gel or aluminium oxide coated onto a piece of glass, metal or plastic, faster and provides more separation than paper chromatography
Stationary phase in thin layer chromatography
silica gel or aluminium oxide, fine powder on glass or plastic
Mobile phase in thin layer chromatography
liquid solvent or mixture such as ethanol or water
Speed of particles in thin layer chromatography
Particles most attracted to the stationary phase move the slowest, Particles most strongly attracted to the solvent move the fastest
How do you know if samples are the same
If they have the same retardation factor
Retardation factor
Value assigned to each component in a sample once the chromatogram is developed, Ratio that expresses how far each component has moved from the origin relative to how far the solvent has moved, taken from distance of starting point to centre of the dot, Distance component travelled from origin/distance solvent from travelled from origin
Gas chromatography
Separation technique for small organic molecules that can withstand relatively high temperatures, Consists of a gas bottle, an oven, a column, a detector and a recorder, Separates compounds with a high vapour pressure and low boiling point
How does gas chromatography work?
Sample is injected into the oven where the unreactive gas pushes the sample into the long, thin column where smaller particles and those that adsorb onto the stationary phase the least leave the column first
Stationary phase is gas chromatography
Long, thin column
Mobile phase in gas chromatography
Unreactive gas such as nitrogen or helium
what is high performance liquid chromatography used for
Used for larger organic molecules that may be unstable to heat
Stationary phase is HPLC
Column (shorter than in gas chromatography)
Mobile phase in HPLC
Liquid that has to be pumped such as water-methanol
Retention time
Time taken for a particular component to pass through the HPLC or GC column, Stronger interaction = longer compound interacts with the stationary phase = longer retention time, Measured by area under the peak of the component- quantitative amount
Calibration curve
Determines concentration of an unknown substance in an unknown sample by comparing the unknown with a known set of standards, Relates to the peaks on chromatograms to the mixture composition
