thin layer chromotagraphy Flashcards
(28 cards)
what does th tlc use as the stationary phase
a chromatography plate consisting of plastic sheet coated with silicon dioxide
why do we use plastic
as they can be cut to the required size using scissor
what do we do with a spot
a small spot contain the mixure of amino acids to be separated is placed on a line using a capillary tube and placed in a tank with solvent
why is a lid place on the tank
so the indide is saturated with solvent vapour
what do we allow to rise
the solvent carrying the amino acids with it
how does the lagging of amino acid depend on
the affinity for the solvent compared to the affinity to the stationary phase dependent of the intermolecular forces between the two
what jhappens when the solvent nearly reaches the top
the plate is removed and the solvent front is marked immediately
as amino acids are colorless what do we use
spray the plate using ninhydride which react to form a purple compound or use uv light
what do we calculate next
rf values for the amino acids that have moved up the p[late
what are the advantages of thin layer chromotagraphy compared to paper
it runs faster
smaller amounts of mixures can be seperates
spots usually spread out a lot less
plates are more robust
what does colum chromotagraphy use
a powder such as silica or aluminium oxide as the stationary phases
what is done to the powder
it is packed into a column
and what happens to the solvent
it is added on the top which included the sample eleunt
what happens to the eleunt
it runs down the colum and the component of the mixure move at different rates
what can be done to these smaples
they can be collected seperately and the time taken to travel through the column
how do we get better seperation
more than one eleunt can be used
why is it an advantage to use this method to seperate
a large amount can be seperated and collected including the pure components
what is the stationary phase in the gas chromotachraphy
powder coated with oil packed or coated in a long capillary tube which is coiled and placed in an overn
what is the mobile phase
an inert gas such as helium
what happens to the smaple
it is injected and carried along by the gas and the mixure seperates in accordance to its retetnaion to stationary phase
what does this mean
hte components leave the column at different times so have different retetnion times
what is done to the dat
it is presented onto a graph with each peak proportional to the amount of component
what is a strenght of using gas chromotagraphy
it is so sensitive it can seperate minute traces in food and crude oil,drug taking
how is the identification of a component done
by matching its retention time with that of a known substance under the same conditions
