chromatography Flashcards
mobile phase
carries the soluble components of the mixture
what relationship between a sample and the mobile phase makes the sample move faster
more soluble components
components with more affinity to the solvent move faster
stationary phase
holds back components of the mixture that are attracted to it
relationship between a sample and the stationary phase that makes the sample move slower
more affinity for the stationary phase means that a component moves slower, often attracted by hydrogen bonding
how are substances separated by chromatography
if suitable stationary/mobile phases are chosen, the balance between affinity for the mobile phase and affinity for the stationary phase is different for each component of the mixture. thus, they move at different rates and are separated over time
advantages of TLC over paper chromatography
runs faster
smaller amounts of a mixture can be separated
TLC plates are more robust that paper
Rf
a measure of the rate of movement of a component through the chromatography apparatus
a ratio between the rate of movement of the solvent and that component
column chromatography
column packed with silica, alumina or resin has solvent run through it
mobile phase in CC
solvent added at the top and runs down the column
advantages of CC
more than one eluent can be used
fairly large amounts can be separated
stationary phase in gas-liquid chromatography
powder, coated in oil. packed into a long, thin, capillary tube. coiled and placed in an oven the temperature of which can vary
mobile phase in GLC
carrier gas, inert
N2
He
advantages of GLC
very sensitive
GLC uses
test athletes
how does GCMS work
GC is run, retention time is recorded, then mixture is run through a mass spectrometer
fragmentation pattern/molecular ion peak confirms identity
