ISOLASI & IDENTIFIKASI SENYAWA KAFEIN DALAM SAMPEL DAUN TEH HITAM (Camellia sinensis)

Summary

This video demonstrates the isolation of caffeine from black tea using various laboratory techniques. The process begins with weighing and soaking tea leaves in water, followed by boiling, filtration, and cooling. Sodium bicarbonate is added, and fractionation is performed using a separating funnel with chloroform to extract the caffeine. The chloroform is evaporated, leaving a yellowish-white powder, which is then crystallized through a simple distillation method. The purity of the caffeine is confirmed using organoleptic testing, microscopy, and Thin Layer Chromatography (TLC), yielding a final product with a purity confirmed by a single spot on the TLC plate.

Takeaways

• 😀 The isolation of caffeine begins with weighing 50 grams of black tea and adding it to a larger beaker glass.
• 😀 The tea is mixed with 300 ml of aquades (water) and heated on an electric stove for 30 minutes, with occasional stirring.
• 😀 After boiling, the tea is filtered through a flannel cloth to separate the tea leaves from the liquid.
• 😀 The filtered tea is then cooled using a cooling bath filled with cold water.
• 😀 Sodium bicarbonate (Na2CO3) is added gradually to the cooled tea, and it is stirred until homogeneous.
• 😀 Fractionation is performed using a separating funnel, where chloroform (75 ml) is added to extract caffeine from the tea solution.
• 😀 The solution is heated to remove the chloroform vapor, leaving behind the caffeine extract in a solid form.
• 😀 The extracted caffeine is then purified using a process called sublimation, which turns the caffeine into a vapor and back into a solid.
• 😀 The caffeine is collected as a white, crystalline powder after sublimation, which is scraped from the dish using a spatula.
• 😀 The purity of the caffeine is verified using organoleptic testing (appearance, taste, and smell), microscopy, and Thin Layer Chromatography (TLC).
• 😀 The TLC test confirms the purity of the caffeine isolate, with only one spot visible on the chromatogram, indicating it is pure.

Q & A

What is the purpose of the experiment described in the script?

The purpose of the experiment is to isolate caffeine from black tea leaves using chemical and physical processes such as extraction, filtration, and sublimation.

Why is a porcelain lid used during the boiling step?

The porcelain lid is used to minimize the loss of vapor during boiling and ensure efficient heating of the tea mixture.

How is the tea extract filtered in this procedure?

The tea extract is filtered using a tea filter and a flannel cloth to separate the liquid from the solid tea leaves (the residue).

What role does sodium bicarbonate (Na₂CO₃) play in this procedure?

Sodium bicarbonate is added to the cooled tea extract to help neutralize any acidic components, making the solution more suitable for further extraction with chloroform.

Why is chloroform used in the extraction process?

Chloroform is used because it is an organic solvent in which caffeine is soluble, allowing it to be separated from the aqueous phase through a liquid-liquid extraction.

What happens during the separation of the two layers in the separatory funnel?

The chloroform layer, which contains the caffeine, settles at the bottom due to its higher density, while the water layer remains on top. The two layers are then carefully separated.

How is the caffeine purified after extraction?

After extraction, the chloroform is evaporated, leaving behind a white-yellowish solid. This solid caffeine is then further purified through sublimation, where it is heated and condensed back into pure crystals.

What is the principle behind the sublimation process used in the experiment?

The principle behind sublimation is that the caffeine transitions directly from a solid to a gas and then back to a solid form, leaving impurities behind.

How is the purity of the isolated caffeine confirmed?

The purity of the isolated caffeine is confirmed through Thin Layer Chromatography (TLC), where a single spot is observed, indicating that the caffeine is pure. Additionally, it is tested using Dragendorf reagent, which produces a characteristic brown spot.

What is the yield of caffeine obtained in this experiment, and how is it determined?

The yield of caffeine obtained is 0.08%. It is determined by calculating the percentage of caffeine recovered from the original tea sample.