Analytical Chemistry

Table 4.16 Typical applications of thin-layer chromatography

Separation Stationary phase Mobile phase

amino acids and peptides cellulose 2 - dimensional

1. n-butanol/acetic acid/water


2. phenol/water
   hydrocarbon oils, ester oils silica gel light petroleum/ether
   simple sugars cellulose n-propanol/ethyl acetate/water
   steroids, e.g. bile acids, estrogens, sterols silica gel chloroform/acetone
   Co, Cu, Fe, Mn, Zn, Ni cellulose acetone/conc. HCl
   alkaloids, e.g. belladonna, morphine, opium, purine silica gel chloroform/ethanol
   chlorinated insecticides, e.g. Aldrin, DDT,
   Heptachlor, Endrin

silica gel hexane

vitamins, e.g. A, D, E silica gel hexane/acetone

B,C silica gel water

Apparatus and Instrumentation

Glass columns for separation by gravity flow; glass, metal or nylon tubing for pressurized systems;
fraction collector, detector and recorder.

Applications

Mainly inorganic, especially mixtures of metals with similar chemical characteristics, e.g. lanthanides;
separation of amino acids.

Disadvantages

Gravity flow separations slow; separated components accompanied by a large excess of eluting
electrolyte.

Ion-exchange separations are limited to samples containing ionized or partially ionized solutes. The
stationary phase consists of an insoluble but porous resinous material which contains fixed charge-
carrying groups and mobile counter ions of opposite charge. The counter ions can be reversibly
exchanged for those of a solute which carry a like charge as the mobile phase travels through the system.
Variation in the affinity of the stationary phase for different ionic species is responsible for differential
rates of migration. Separations are often enhanced by eluting with a mobile phase containing a
complexing agent.