UV Visualization

None required (TLC plates must contain a UV indicator).

Compounds with chromophore groups.

p-Anisaldehyde

Mix 15 mL acetic acid and 3.5 mL p-anisaldehyde into 350 mL ice-cold ethanol. Slowly add 50 mL of concentrated sulfuric acid dropwise over 60 minutes. Store at 0°C.

Allylic alcohols (green), phenols (violet), aldehydes, ketones, carbohydrates, and esters (blue/red). Alkenes, alkynes, and aromatic compounds are not detected.

Bromocresol Green

Dissolve 0.04 g bromocresol green in 100 mL ethanol. Add 0.1 M sodium hydroxide dropwise until pale blue.

Acidic groups with pKa < 5.

Cerium Molybdate (CAM or Hanessian’s stain)

Dissolve 0.5 g cerium ammonium sulfate dihydrate and 24 g ammonium molybdate tetrahydrate in water. Add 28 mL of sulfuric acid and stir for 1 hour.

Universal stain. More sensitive than PMA stain.

Cerium Sulfate

Prepare an aqueous solution with 10% cerium (IV) sulfate and 15% sulfuric acid.

General stain; effective for alkaloids.

2,4-Dinitrophenylhydrazine (DNP)

Dissolve 12 g DNP in 60 mL of sulfuric acid, 80 mL water, and 200 mL of 95% ethanol.

Specific for aldehydes and ketones.

Iodine Vapor

Place iodine crystals in a sealed chamber.

Good for alkanes, phosphines, and thiols.

Ninhydrin

Dissolve 0.3 g ninhydrin in 100 mL n-butanol. Add 3 mL acetic acid.

Specific stain for amino acids and primary amines. Secondary amines stain light yellow; tertiary amines do not stain.

Phosphomolybdic Acid (PMA)

Dissolve 10 g PMA in 100 mL of ethanol.

Universal stain (light-sensitive); does not detect some amines, amides, or oxidation-resistant aromatics.

Potassium Permanganate (KMnO4)

Dissolve 1.5 g potassium permanganate, 10 g potassium carbonate, and 1.25 mL 10% sodium hydroxide in 200 mL water.

Universal stain; detects oxidizable compounds like alcohols, ethers, esters, and alkenes (brown-yellow spots). Reductive compounds like thiols appear white.