I see what you mean. There just seem to be so many undefined variables in these type of articles. Robusta has 4 times(?) the caffeine od arabica and we don't know what beans they are basing their facts on. It would be nice to get some proper scientific facts for what I drink. For a given bean (ignoring the small variations of bean variety) type there must be am ammount of caffeine per g, and the average ammount of caffeine disolved by different brewing processes must be known, so surely it is possible to remove a lot of the variables, and get an accurate result. None of these articles that I have read seem to do this.
This reminds me of specs I see for audio amplifiers that quote say 150W of power without saying whether this is peak or RMS, at what distortion level it is measured, what impedence load, and at what frequency it is measured, without these the power figure is utterly meaningless.
Sorry, rant over articles over
I just like to see proper facts. If I believe the above articles figures then I am in trouble, drinking a cappuccino at breakfast (made with a double) and a double espresso in the evening that's 800mg!
Cheers,
Simon