seperating of species by TLC Flashcards
1
Q
What is the stationary phase and what is the mobile phase?
A
- stationary is either:
- aluminium oxide
- silicon(IV) oxide
- silica gels
- mobile phase is the solvent
2
Q
How is the plate prepared before the solvent ?
A
- draw a pencile line, wearing glvoes, 1.5cm from the bootom of the TLC plate and marks spots for each sample
- place a drop solid on a watch glass and dssolve a few drops in a solvent such as ethanol
- use capillary tube to place a spot on the pencile cross
- allow spot to dry and repeat 3 times, ensuring the diameter of the dot is no more than 0.5cm
- productes a concentrated spot
3
Q
Why are glvoes used? why is pencil used
A
- prevent contamination from the hands
- pencil line will not dissolve in the solvent
4
Q
Why is a tiny spot used?
A
cause different spots to merge
5
Q
What is done with the solvent?
A
- place solvent in a beaker/developing tank to a depth of 1cm
6
Q
How is the chromatogram produced?
A
- place the TLC plate in the beaker/tank and cover with a lid
- allows the solvent to run up the chromatography plate for about 30 minues
- when it has almost rteached the top of the plate, remove from the beaker and mark the line of the solvent with a pencile
7
Q
How is the chromatogram observed?
A
- place plate in a fume cuboard until all the solvent has evaporated and the plate is dry
- if it is colourless:
- place the plate under the UV lamp and mark the location of these substances using a pencil
- in a fume cuboard, place the plate in a beaker contaaining iodine crystals and cover with a watch glass
- iodine is locating agent, causes spots to become brown
- spray with ninhydrin developing agent, in a fume cuboard
8
Q
How are Rf values measured?
A
- measure the distance from the pencil line to the spot, and measure the distance from the pencil line to the solvent front
- calculate the Rf value of each substance visible on the plate and compare to the data book.
9
Q
What are the precaution when using UV light
A
do not look directly into it
