Question

Advertisements for a new espresso maker claim that by increasing the temperature of the water pushed through the coffee grounds that it can significantly increase the concentration of caffeine in the resulting espresso. To determine if the claim is fraudulent and prior to accepting this claim, what type of evidence would you like to see? Provide details of an investigative design.

Answer 1

The solution deals with the solubility test for caffeine and shall require the following procedure -
1. Heat water to temperatures of 25 ^oC, 40 ^oC, 50 ^oC, 60 ^oC, 70  ^oC, 80  ^oC, 90 ^oC, and 100  ^oC, and have the same amount of water, let's say 20 ml in different beakers.
2. Ground coffee beans from the same batch, and weigh them as 5g each and keep it in a funnel on a filter paper.
3. For every single run of water, collect the filtrate in a beaker and mark it with the respective temperature.
4. Note that amount of time taken for different temperature samples of water must be same, since over a longer time, more caffeine maybe dissolved and come in the solution.
5. Now, that caffeine-water collected in the beaker can be used to go for further tests.

Further tests can be done as Thin Layer Chromatography where the detail can follow as -
1. On a TLC strip mark a line and points where the liquid is to be put.
2. Now, put a very small amount using a capillary tub.
3. Observe after a while.

The results will be that for the highest concentration, the blot that is formed will be the largest.

Now, based on the available values, the solubility of caffeine in water is 2 g/100 ml at Room Temperature and 66 g/ 100 ml at boiling point of water, thus, it cam be seen that higher the temperature of water, more is the solubility of caffeine.

For quantitative methods, Iodometric Titration maybe done in a standard sodium thiosulphate solution in acidic medium.