exp 4 Flashcards
CHROMATOGRAPHY
- encompasses…?
- encompasses variety of techniques for separating individual compounds or compound types from a mixture
SEPARATION in chromatography is affected by the ____ of the _____ of a given mixture between a ______ phase and a _____ phase
affinity
compounds
stationary
mobile
2 types of CHROMATOGRAPHY
- Adsorption
- Partition
ADSORPTION CHROMATOGRAPHY
- uses what 2 phases?
- separation is thru what process?
- uses a SOLID stationary phase and LIQUID mobile phase
- through SURFACE ADSORPTION PHENOMENA
PARTITION CHROMATOGRAPHY
- uses what 2 phases?
- the 2 phases must be??
- separation is thru what process?
- uses LIQUID stationary phase & SOLID AND LIQUID or GAS mobile phase
- insoluble to each other
- through differences in the solubility of the sample in the stationary and mobile phases
PROCESS of adsorption chromatography (3 steps)
- mixture to be separated is placed (adsorbed) on solid stationary phase
- the liquid mobile phase is allowed to flow
- the individual components of the mixture to be separated will move at different rates = evident in separate regions (bands/spots) in the stationary phase
The ____ of the _____ compound between the ____ phase and ___ phase is an _____ process
transfer
adsorbed
stationary
mobile
equilibrium
ADSORPTION CHROMATOGRAPHY
- the extent of adsorption of a single component depends on… (3)
wherein the more _____ the compound to be separated is, the ______ it will be _____ on the surface of the ______ _____ phase
- polarity of molecule
- activity of adsorbent
- polarity of liquid mobile phase
polar
more strongly
adsorbed
polar stationary
ADSORPTION CHROMATOGRAPHY
the actual separation of the _____ in the mixture to be separated is dependent on….?
COMPONENTS - dependent on the
RELATIVE VALUES of the ADSORPTION-DESORPTION EQUILIBRIUM constant, K, for EACH of the components
ADSORPTION CHROMATOGRAPHY
- most common example?
- ^ is a form of ________ adsorption chromatography that uses a ________ of _______ supported on a _______ as stationary phase
- most common adsorbent (2) and stationary phase (2) used
- Thin-layer chromatography
- solid-liquid adsorption
- thin layer of adsorbent
- flat surface
- alumina
- silica gel
- glass
- aluminum
THIN-LAYER CHROMATOGRAPHY
importance (5)
- useful in monitoring the progress of reactions
- detecting intermediates in reactions
- analyzing crude products/unknown mixtures
- determining the number of components in a mixture
- evaluating the efficiency of purification processes
what PARTITION CHROMATOGRAPHY is similar to TLC?
- how is it different in terms of principle
- materials used?
- importance? (2)
Paper Chromatography
- uses liquid-liquid partition chromatography
- FILTER PAPER: made of highly purified cellulose, thus, absorbs and retains water molecules strongly
- used in rapid analysis of the components of a reaction mixture AND as a tentative means of identification
What compound is an example of a HIGHLY PURIFIED CELLULOSE?
polyhydroxy
PROCESS of PARTITION CHROMATOGRAPHY (3)
- Small spots of mixture to be separated is placed at bottom of filter paper OR TLC plate
- The liquid (solvent) mobile phase travels up the paper thru capillary action AT A RELATIVE RATE TO THAT OF THE SOLVENT FRONT
- Bands/Spots also appear for each component of the mixture
PARTITION CHROMATOGRAPHY
separation takes place due to the __________ of the _____ of the mixture for the _________ phase and ______ phase
wherein there is a _____ of ______ between the 2 phases, but those components that are _______ in the ______ phase will???
different affinities
components
polar stationary phase
nonpolar mobile phase
continuous exchange
solutes
more soluble
mobile
will spend more time in it and carried up faster
what described the relative mobility of the compound?
and what formula does it use?
Retention Factor, Rf
= (distance travelled by compound from origin) / (distance travelled by solvent from origin)
where origin is midpoint of the original spot
how to obtain distance traveled by a compound?
measure distance from origin to point of greater density of the spot corresponding to compound
when can Rf be used for identification of a compound?
under a definite set of conditions (adsorbent, solvent, temperature, humidity)
