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THIN LAYER CHROMATOGRAPHY - Coggle Diagram
THIN LAYER CHROMATOGRAPHY
DEFINATION -
is a method for analyzing mixtures by separating the
compounds in the mixture. TLC can be used to help determine the number of components in a
mixture, the identity of compounds, and the purity of a compound
THEORY -
spotting, development, and visualization.
First the sample to be analyzed is dissolved in a volatile (easily
evaporated) solvent to produce a very dilute (about 1%) solution. Spotting consists of using a micro
pipet to transfer a small amount of this dilute solution to one end of a TLC plate, in this case a thin
layer of powdered silica gel that has been coated onto a plastic sheet. The spotting solvent quickly
evaporates and leaves behind a small spot of the material
APPLICATIONS -
Analysis of drug residues and antibiotics in food and environmental samples
Identification and quantification of colors, ingredients, preservatives, and sweetening agents in food and cosmetic products
Quality control and purity testing of pharmaceutical formulations
Rapid, high-throughput screening prior to HPLC
Examination of chemical reactions for completion
INSTRUMENTATION -
Thin Layer Chromatography Plates – ready-made plates are used which are chemically inert and stable. The stationary phase is applied on its surface in the form of a thin layer. The stationary phase on the plate has a fine particle size and also has a uniform thickness.
Thin Layer Chromatography Chamber – Chamber is used to develop plates. It is responsible to keep a steady environment inside which will help in developing spots. Also, it prevents the solvent evaporation and keeps the entire process dust-free.
Thin Layer Chromatography Mobile phase – Mobile phase is the one that moves and consists of a solvent mixture or a solvent. This phase should be particulate-free. The higher the quality of purity the development of spots is better.
Thin Layer Chromatography Filter Paper – It has to be placed inside the chamber. It is moistened in the mobile phase.
DISADVANTAGES -
Thin Layer Chromatography plates do not have longer stationary phase.
When compared to other chromatographic techniques the length of separation is limited.
The results generated from TLC are difficult to reproduce.
ADVANTAGES - rapid analysis time because many samples can be analyzed simultaneously, low solvent usage on a per-sample basis, a high degree of accuracy and precision for instrumental TLC, and sensitivity in the nanogram or picogram range
RETENTION FACTOR - The retention factor, or Rf, is defined as the distance travelled by the compound divided by the distance travelled by the solvent.
The Rf for a compound is a constant from one experiment to the next only if the chromatography conditions below are also constant:
solvent system
adsorbent
thickness of the adsorbent