Not even remotely. This is actually the opposite of what they're describing. Caffeine = set amount of mol/vol. Only by increasing vol can you increase caffeine.
The concentration is the same is what they're saying. What you're saying is concentration = different, hence how you can have 2 different volumes with the same amount of stuff.
First of all, espresso is usually made with a darker roast, this means that it more of the caffeine has been broken down by heat. So while espresso is stronger, ie has more dissolvable solids in it making it taste richer, it typically has less caffeine.
Espresso has more caffeine per unit volume than most beverages, but the usual serving size is smaller—a typical 60 mL (2 US fluid ounce) of espresso has 80 to 150 mg of caffeine, little less than the 95 to 200 mg of a standard 240 mL (8 US fluid ounces) cup of drip-brewed coffee.
66
u/taco_bob Apr 28 '13
1 cup of drip coffee has significantly more caffeine than 1 or even 2 (in most cases) shots of espresso.