The question "What reagent is used in TLC?" is a bit too broad, as various reagents are used in Thin Layer Chromatography (TLC) depending on the specific purpose. It's more accurate to ask, "What type of reagent is used in TLC for visualization?" or "What specific reagent is used for a specific purpose in TLC?". We will address both to clarify the answer.
Visualization Reagents in TLC
TLC is often performed with clear glass plates. Many compounds are colorless, making it hard to visualize the separated components of a sample. Therefore, visualization reagents are needed to make these spots visible. These reagents can be categorized into:
- UV-Active Substances: Compounds can be detected under UV light, usually at 254 nm or 365 nm, if they are UV-active or contain a UV-absorbing indicator (e.g., a fluorescent indicator mixed in the silica gel of the TLC plate).
- Staining Reagents: These reagents react with the compounds on the TLC plate, forming colored products. These include:
- General Staining Reagents: For example, iodine vapor is a common reagent that reacts with many organic compounds, resulting in brownish spots.
- Specific Staining Reagents: These are used to detect specific classes of compounds, for example, ninhydrin for amino acids.
- Charring Reagents: These reagents char the organic compounds on the TLC plate, forming black or brown spots. This is often done by heating the plate after applying the charring reagent.
Example: Charring Reagent From the Provided Reference
According to the reference given:
Used as a charring reagent for polymer bound TLC plates (the newer hard layer plates) Spray with a solution of 2g FeCl3 in 83ml n-butanol and 15ml conc. sulfuric acid.
This highlights a specific charring reagent made of:
| Component | Function | Concentration |
|---|---|---|
| Ferric Chloride (FeCl3) | Acts as a catalyst / oxidizer | 2 g |
| n-Butanol | Solvent | 83 ml |
| Concentrated Sulfuric Acid (H2SO4) | Charring agent. Concentrated acids serve to dehydrate and oxidize organics, leading to carbonization. | 15 ml |
This specific reagent is useful for polymer-bound, hard-layer TLC plates. The concentrated sulfuric acid acts as a charring agent, while the ferric chloride (FeCl3) and n-butanol act as a catalyst/oxidizer and solvent respectively, aiding the charring process.
Summary
The original question, "What reagent is used in TLC?" does not have a single answer. Here's a breakdown:
- Visualization reagents are used to make the separated compounds visible.
- Various types of reagents (UV active substances, staining reagents, and charring reagents) can be used.
- Specific reagents are chosen based on the type of compounds being separated and the method of visualization desired.
The provided reference highlights one specific charring reagent: a solution of ferric chloride, n-butanol, and concentrated sulfuric acid, used for visualizing components on polymer-bound TLC plates.
