Chromatography Flashcards
What is chromatography
Analytical technique used to separate and identify component molecules in a mixture when dissolved in fluid (mobile phase) flow through another material (stationary phase) at varying rates
What is retention time
Time it takes a substance to pass through the column
What does rate of separation depend on
How the components in the mixture interact with the stationary phase (their retention) and how soluble they are in mobile phase and which they are more attracted to
What is stationary phase in TLC
Thin metal sheet coated in layer of silica
What happens in stationary phase of TLC
Solute molecules adsorb onto surface and depending on the strength of interaction with stationary phase will travel particular distances through the plate
What is mobile phase of TLC and what happens in it
Polar/non-polar solvent that carries components being investigated and flows over the stationary phase
How to locate AAs on chromatogram
Ninhydrin
How to calculate Rf value
Distance travelled by component/distance travelled by solvent
What does TLC stand for
Thin layer chromatography
How to separate dots which overlap in TLC
Rotate sheet through 90 degrees and use second solvent which will further separate them
What is stationary phase in column chromatography and how is it arranged
Vertical column packed with solid powdered substance eg silicon dioxide
What is mobile phase in column chromatography
Liquid solvent which is added into the column until it is saturated with solvent
What is solvent and component mixture called in column chromatography
Eluent
What happens once sample added in column chromatography
More eluent added do it doesn’t dry out, sample flows through column via gravity
What component will take longest time to flow through column
Component with the greatest attraction to the stationary phase
What does time taken to move down column in column chromatography depend on
Balance between solubility of each substance in mobile phase and it’s retention in stationary phase
What is column chromatography usually used to separate
Coloured substances
What does HPLC stand for
High performance liquid chromatography
How is HPLC dif to column
-doesn’t work via gravity but sample pumped through by solvent
-particles of stationary phase smaller leading to greater separation of compounds and thin tube used packed
-detector at end of column which measured retention time
-automated so results obtained quicker
What is retention time in HPLC
Time taken from sample being injected to sample being detected
What is gas chromatography used to separate
Volatile liquids
What is stationary phase in GC
Long coiled column of non volatile liquid
What is mobile phase in GC
Inert carrier gas eg helium/nitrogen which moves the sample molecules through stationary phase
What substance detected first in GC
Most volatile substance
