Flashcards in Chromatography Deck (10):
describe: mobile phase, stationary phase, origin
origin is the original posiiton of the substance. it needs to be above the mobile phase at first so it wont dissolve into it.
what happens to components, stationary phase and mobile phase during chromatography?
components are swept up over the stationary phase by the mobile phase. during this, there is a constant process of adsorption and desorption
define: adsorption and desorption
o Adsorption: adhesion of substances to the surface of the stationary phase
o Desorption: breaking of bonds between substance and surface of solid/liquid (and dissolving into the mobile phase)
why do components separate?
because substance adsorb/desorb to the stationary phase at different rates based on their attractions to them.
qualitative analysis techniques for chromatography?
same conditions: run them side by side. same chromatograph = probably same compound.
calculate retardation factor under the same conditions: distance component goes/distance from solvent front.
describe column chromatography.
column is filled with a packed solid.
put sample on top
resevoir drips mobile phase onto it.
as the moile phase moves down, adsorption and desorption occurs at different rates, enabling splitting of components.
tap lets out eluent at the same rate as the mobile phase enters.
how is HPLC different from column chromatography
there's a pump, injector, detector and recorder.
stationary phase is silica or alumina - smaller - larger sa - more frequent adsorption/desorption -better separation - more sensitive analysis
pump bc theres more resistasnce to flow of mobile phase.
stream is also passed through UV light, detector measures absorbance and recoded on chromatogram
how long it takes for a component to pass throguh the column
same compounds will ahve the same retention time under the same conditions