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Dalal AND 4) Students typically achieve a percent recovery of <70%. Where is the remaining 30%? Go through the procedure thoroughly and list at least 4 places where you definitely lost caffeine. IN OF

Procedure Solid-Liquid Extraction - Brewing the Tea 1. Obtain two tea bags. Weigh both tea bags and the contents on an analytical balance to 0.0001 g. The mass of empty tea bags will be provided to you in-lab. Use the provided mass to calculate the mass of tea leaves in your bag. 2. In a 250 mL beaker, add 2 boiling chips and boil approximately 75 mL of distilled water. When the water has boiled, remove the beaker from the heating plate and add the pre-weighed tea bags to brew the tea for at least 3 minutes. Once the tea is steeped, remove the tea bags to a watch glass, place a second watch glass over, and squeeze the excess tea extract into the beaker. 3. Prepare a TLC plate while waiting for the tea extract to cool in an ice-water bath. 4. Once the tea extract has cooled down to room temperature, use a capillary tube to draw up a sample of tea extract. Spot the tea extract (about five spots and let dry after each application) on the TLC plate. Check the size and intensity of the spot with the UV lamp before proceeding. Liquid-Liquid Extraction - Extracting Caffeine into Dichloromethane 5. Transfer the cold tea extract to a separatory funnel and leave the boiling chips behind. Extract the tea extract with two portions of 15 mL dichloromethane. NOTE: Agitate the contents in the separatory funnel without shaking it too vigorously or a the bun cloar

Liquid-Liquid Extraction-Extracting Caffeine Into Dichloromethane 5. Transfer the cold tea extract to a separatory funnel and leave the boiling chips behind. Extract the tea extract with two portions of 15 mL dichloromethane. NOTE: Agitate the contents in the separatory funnel without shaking it too vigorously or a thick layer of emulsion will form. If an emulsion is formed between the two clear layers, break the emulsion by swirling the separatory funnel gently or stir the contents using a clean glass rod. 6. Discard the aqueous (tea) layer after extracting twice with dichloromethane. Rinse the stopper and funnel with a little distilled water. 7. Return the organic (dichloromethane) layer to the funnel and add 10 mL of 5% NaOH solution. Shake, allow the layers to separate, and collect the dichloromethane layer. Discard the NaOH layer and return the dichloromethane extract again to the funnel. Repeat the extraction once more with 10 mL of 5% NaOH. 8. Return the dichloromethane extract to the emptied funnel, and wash (shake) the organic layer with 20 mL of distilled water. Extract and collect the organic layer in to a clean and dry 150 mL beaker. 9. Add anhydrous sodium sulfate drying agent to the organic layer beaker. Swirl the solution. It should be very clear once dried. NOTE: Do not add too much drying poopt or it may physically absorb all of the liquid.

10. Weigh a clean and dry 100 mL round bottom flask (RBF). NEVER PUT AN ADHESIVE LABEL ON RBFS - they will absorb water and change the mass of the flask. Set up a gravity filtration with fluted filter paper and glass funnel supported by a ring clamp. Place the pre-weighed 100 mL RBF so that the end of the stem of the funnel is within the RBF to prevent splashing and loss of the product. Filter the dried organic layer. 11. Use a capillary tube to draw up a sample of the dried organic layer. Spot this crude caffeine sample on the TLC plate. Check the size and intensity of the spot with the UV lamp before proceeding. 12. Remove the dichloromethane layer using the rotary evaporator. 13. When all of the dichloromethane has evaporated, remove the 100 mL RBF from the rotary evaporato Dry the bottom of the RBF. Reweigh the RBF and crude caffeine, once it has cooled to room temperature. 14. Discard the remaining crude caffeine in the appropriate waste container. Thin Layer Chromatography