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INTRODUCTION TO CHROMATOGRAPHY - Coggle Diagram
INTRODUCTION TO CHROMATOGRAPHY
types of chromatography
column chromatography
how
we have a packed of column with beads , the pour the liquid mixture
the polar components at the liquid will attach move to polar beads, wich mean they will travel more slowlydown the column
other things will travel more quickly
stationary phase
polar based , there a beads within a packed column
mobile phase :
liquid phase : mixed with several difference organic compound contain within a liquid that often time is dissolved in either or sometimes will dossolve in other thing
notes
"elution" explaim about the escape of components from the column . it sees how quickly it moves throughand escape column
conclusion
-the more polar component , more slowly it will move because it will continuosly react with that stationary phase of those polar beads
TLC/paper chromatography
how
mixed up unknown compound , place little dots on a line on the TLC
2.put in beaker containing solvent (ether),ether will travel or migrate up the paper quickly
3.this material will caught up the ether solvent and solvent will continue travel up the paper .
stationary phase
-paper
absorbent paper
-TLC
glass/plastic with attach absorbent material on surface
mobile phase
liquid mixture in solvent(use ether )
notes
-if component B less polar , the solvent will quickly move up the paper
-if it travel less , the component is more polar
gas liquid chromatography
how
column
*injection
-mixture of sample +carrier gas is injected
after inject ,it will travel to the column
some less will interact ith the liquid which means it is less polar , it will elute quickly move and reach the detector first
a lot of other parts wont interact very much with the liquid (elute move slowly and it is more polar )
detector
stationary phase
liquid that is somehow attached to a packed column
mobile phase
gas + mix with some carrier gas
*carrier gas : inert , wont interact with compound but can help cary the component
conclucion
the less polar of component , it will travel more quickly
terminology and general types of chromatography
:star: :terminology
-stationery phase is in column
-eluent in ->COLUMN -> eluent out (elution process)
-column can be packed or open tubular
:star: :principle of separation
-component of the mixture that are strongly retain on stationary phase move slower than weakly retained component
-component separated into discrete band
-rate of band migrate depends upon the fraction of time its spend on mobile phase
:star: chromatogram
-a plot of detector response vs. time
-detector respons to analyte as it is used eluted from the end of the column.
interaction of analyte and mobile stationary ,mobile phases .
:star: migration of analyte in column
equilibrium of analyte between stationary phase and mobile phase
-distribution constant (K), is concentration of analyte in stationary phase over in mobile phase
-Retention time is length of time from
sample injection until analyte reach detector
-dead time is length of time for unretained species to pass through the column
-adjusted retention time is the actual time analyte is retain on the column whic is retetion time minus dead time
:star: retention factor(k')
-important parameter to describe migration rates
-k'=retention time minus dead time and over dead time
:star: relative rates of migration
-the selectivity factor (alpha)= retention factor of analyte A over B
-a figure of merit that reflect the selectivity between analyte in mixture
factors affecting separation efficiency
band broadening and column efficiency
:star: peak shape
-shaped like gaussian distribution
-peak of the curve represent the average time an analyte spends on the column
-the longer the column , the wider the peak
-the higher the flow rate, the narrower the peak
:star: column efficiency
-performance characteristic that describe how a column separated component in mixture
-plate theory :contain a series of plates in which analyte move from 1 plate to the next using eqm pocess
-plate number(N) is length of column packing(L) over height of plate (H)
:star: Experimental determining of H and N
-standard deviation as a function of time
-time standard deviation is standard deviation over (L/retention time )
-H = LW2/16(retention time)2
-N=16(retention time /W) 2
:star: zone broadening
-flow rate LC<GC because mobile phase is more slowly in LC
-plate height LC<GC
-LC is more efficient due to small height plate
:star: A term :multiple flow paths (Eddy difussion )
-variety of routes that solutes molecule can take .the broaden the peak
-not change with time spent in column
-for better smaller H:
diameter of packing particle should be small
A=0 for open tubular
:star: B term :longitudinal diffusion
-the more time spent in column , the more important diffusion from high to low concentartion becomes .
-for better H smaller:
increase flow rate
smaller diffusion coeficient in the mobile phase
:star: C term : equilibration time (mass transfer)
-the faster the mobile phase , the worst mass transfer
-fast equilibration:(mobile solute will not get to afar from stationary)
by thinner sorbent layer on stationary phase
raise temperature
comparing open tubular and packed column
:star: open tubular advantages :
-better resoltuion
-less longitudinal difussion
-increase sensitivity and lower sample capacity
-keep tubes narrower ans stationary phase thin so that C term is not large
Resolution
:star: column resolution(Rs)
resolution=(∆t_r)/w_av
=(∆V_r)/w_av =(0.589∆t
r)/w
(1/2 av )
-the ideal of resolution is between 1.5 and 10
-resolution that greater than 10 is wasting time with no real benefit
:star: ways to improve
-increase N
-change retetention factor (change T in GC )
-change selectivity factor
general elution problem
:star: elution problem :
-dificult to find elution parameter
-use gradient elution or solvent programming in LC or temperature programming for GC.
:star: qualitative analysis
-have characteristic retention time molecules
-one piece information on its detection
-have peak at a retention time os not confirmation that the peak will represent the molecule, it can be others as well.
-the peak i s also not confirmation for the existence of the molecule
-the absence of peak indicates the compound is either absent or below the detection limit.
-chromatography not tell many things about molecule as it is just separation tool that need to be pair with other specific :
:star: quantitaive analysis
-have detector responding to eluting compounf, use peak heigt /peak area to obtain amount of material
-peak area over the peak height
-perform a calibration curve with a series of different concentration of standard
-variation and sample volume inject