Second experiment (Michael)

Here is my second experiment of my project! Caffeine, as one of the major compounds presented in a cup of coffee, there are so many coffee lovers rely on it to make them refreshed for a whole day. The following experimental procedures, designed based on the procedures suggested by Chemistry LibreTexts website, aim to find out the relationship between the water temperature and extraction efficiency of caffeine. (With my supervisor's permission, the following experiment was conducted in laboratory.)

Experimental setup and procedures

Objective

Find out the effect of water temperature on the extraction efficiency of caffeine during the brewing step

Hypothesis

The extraction of efficiency of caffeine will increase with higher water temperature brewing as predicted by Arrhenius equation.

Sample

Maxwell House Drip Coffee (Blue Mountain Flavour) with coffee filter bag

Apparatus

Beakers, conical flasks, droppers, spatula, balance, extraction funnel, funnel, stir bars, heat plates (with stirring function), thermometers, round bottom flasks and rotary evaporator.

Materials

Tap water, ground coffee sample, potassium carbonate powder, ethyl acetate (AR grade), acetone (AR grade), distilled hexane.

Procedures

1. Boil 200 mL water to 100^oC with a conical flask, stir bar, thermometer and heating plate

Figure 1: The setup for boiling water

2. Pour water over the filtration bag provided by the sample coffee (contains 10g of ground coffee), and collect the coffee (filtrate) to a beaker

3. Add about 5g potassium carbonate to the solution and stir it for 10 minutes

Figure 2: Potassium carbonate powder

4. Extract the solution with ethyl acetate for three times

5. Combine the organic layer and dry it with rotary evaporator

Figure 3: Rotary evaporator

6. Recrystallize the crude solid product with hot acetone and hexane

7. Collect and weight the resulting solid

8. Repeat step 2 to step 7 with ice water

Experimental data

Figure 4: The final coffee products (From left to right are the coffee products brewed with 0 and 100 ^oC water respectively)

Figure 5: The final extracted caffeine products (Left = coffee brewed with 0 ^oC water; Right = coffee brewed with 100 ^oC water)

Amount of water added (mL)	Amount of ground coffee (g)	Temperature of water (oC)	Amount of extracted caffeine (mg)
200	10	0 (ice water)	29.6
200	10	100	37

From the experimental data, the extraction efficiency of caffeine increases for 25 % with the water temperature at 100 ^oC comparing the one at 0 ^oC. This agrees with the assumption made in the beginning. However, the recrystallization is not very successful, and therefore the measured amount of extracted caffeine may not be very accurate.

Reference

1.  Extraction of caffeine (experiment). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Ancillary_Materials/Laboratory_Experiments/Wet_Lab_Experiments/Organic_Chemistry_Labs/Experiments/3%3A_Extraction_of_Caffeine_(Experiment)

By Lee Ki Wai (Michael) 3035374450