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Sulphuric acid10% Sulphuric acid in ethanol is suitable for the detection of most polar compounds such as carbohydrates. After dipping or spraying with the reagent the TLC plate is heated and many compounds are charred to give grey or black spots. Quantification is difficult since prolonged heating tends to give a dark background.Some compounds, such as amino sugars, give only weak spots despite dehydration. In the case on amino sugars this is due to the formation of volatile nitrogen heterocycles. Reagent (100mL)Slowly add 10 mL conc. sulphuric acid to 90 mL ethanol. The resulting solution can become very hot, in particular if larger amounts are prepared!Reagent (1000mL in water)For spraying the ethanol can be replaced with water. In that case take a 1000mL measuring cylinder and fill it with crushed ice. Add 100mL conc. sulphuric acid. The ice should now melt. Add water to 1000mL. |