Page 83 - Instrumental Analysis - Pharm D Clinical- 07-PA403

Practical steps 75

• A very small amount of a solution of
the substance to be analyzed is
applied in a small spot with a capillary
tube (or microsyringes), ~1cm from the
bottom of the TLC plate.

• The TLC is developed in a jar which
contains the developing solvent (the
mobile phase).

• As the mobile phase rises up the TLC
plate by capillary action, the
components dissolve in the solvent
and move up the TLC plate.

• Individual components move up at
different rates, depending on their
affinity to the stationary phase.

• Spots of the different components are
detected

Prof. Omayma Abdelrazak Amin

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Locating analytes on the plate

a) Colored substances can be seen directly when viewed against
the stationary phase

b) colorless substances can be detected by various ways including:
• Ultra-violet (UV)detection: exposure to UV light, spots appear
dark on a lighter background.

• Iodine Vapour: spots become brown
• Spraying the plate with an appropriate reagent to give colored

spots

Prof. Omayma Abdelrazak Amin 76

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