What method of coffee preparation gives the most caffeine in the finished cup?

Question

As the question asks, which method from the list below will give the most caffeine in the final product (ie. a cup of coffee). Assume the same beans with the same grind (while the different techniques should use different grinds, lets try and keep things simple) and as much as possible assume things are kept constant - Aiming for a 200ml cup of coffee made from (if appropriate) a double shot of espresso, the rest made up by water. :

1. Professional Espresso maker (i.e. in a coffee shop)
2. Aeropress
3. Stovetop espresso maker
4. French Press
5. Consumer grade capsule coffee machine (e.g. nespresso). Once again assume that we can find the same bean in a bought capsule.

Answer 1

This question is nearly unanswerable. Typical caffeine content data is given as a range based on the normal brewing factors of each method, there isn't data for abnormal methods i.e. french press with fine grind or espresso with coarse grind.

Typical caffeine contents:

• 3oz Espresso double shot: 70-200mg
• 8oz drip: 60-100mg
• 6oz French Press: 80-100mg
• 6oz Aeropress: 60-80mg

On average the espresso or moka pot coffee would have significantly higher caffeine concentration than other methods (with the moka pot maybe edging out the espresso because it uses higher temperature for extraction). There is so much variability that I don't know if there's any point in trying to answer this question. The article linked below shows that one method alone (espresso) can yield shots with caffeine concentrations that are radically different:

The extended range of caffeine values found in retail coffees in this study suggests that it is presently not possible for individuals interested in assessing the caffeine content of their diet to do so if the intake includes retail coffee. Our data highlights that, if just two retail coffees are consumed in a day by the same individual, that a variance of more than 290 mg can occur if both of these espressos are purchased from either the highest or lowest 10th percentiles of all the beverages sampled

If you control for volume by diluting everything with a typical serving size less than 200mL, all the methods are going to yield caffeine doses in the range of 60-100mg. A typical espresso based Americano (1 shot + water to make 5oz) would also fall in that range.

http://www.aseanfood.info/Articles/11020406.pdf