I've found some methods to analyze the caffeine content of a water brew, but I don't have a chemistry lab, and I'm not a chemistry geek. If I bought some chemicals I could probably handle it, we have a gram scale somewhere, but I know myself well enough to guess that my lazy accuracy would not get me a good enough result. So that's out, and I'm back to trying different search terms to find the research that surely someone else has already done.
"caffeine content by brewing time" finally got me this article which had some interesting measurements:
1. The caffeine content decreased dramatically from the first to the third brew, about 50-70mg/cup in first cup, 15-25 in second, and 5-10 in third, each brew about 5 minutes in length.
Which contradicts the pre-brew for 30 seconds method of decaffeination - to get the 90% caffeine reduction for 'decaf' you'd have to pre-brew for 10 minutes, which would give you pretty watery tea.
2. All teas [black,green,oolong] have roughly similar caffeine contents
It goes on to assert that green tea does not have 1/3 the caffeine content of black tea. I should go look up the original source. $31.50, for something published in 1996. Ridiculous.
Well, my research concludes that I should just enjoy a cup of awesome sencha once every couple of days, re-brew those leaves a couple times if I want, and drink carbon dioxide decaffeinated tea the rest of the time. Pre-brewing for caffeine removal is pretty useless, especially since I think the tea tastes comparatively awful afterwards. Apparently my favorite flavonoids are highly water soluble. Wait, does that mean I should just go ahead and drink the first 30 second brew to reduce my caffeine? huh. I still need a real data curve.
Other good articles:
Upton Tea Imports: Newsletter - Winter 2003: Tea and Caffeine
Someone's extrapolation of some caffeine vs brewing time
ooooh: Results of the Asbury College Study on Tea Caffeine (on the right side of the page.) More data. Their averages work out to 60mg, 24mg, and 9mg for subsequent 3minute brews, and support the assertion that there isn't any basic difference in caffeine content between white, green, and black teas.
Caffeine and Tea: Myth and Reality A good overview article.
Where was I? I have a cold. For less caffeine, use fewer leaves, larger leaves rather than smaller ones, don't brew as long, if you are going to have multiple cups rebrew the same leaves, or drink decaf. I didn't find any data on brewing temperature, other than caffeine is extracted more slowly at lower temperatures, but the real question is whether the rest of the tea flavors also slow down the same or more or less. I guess I'm going to try a 30 second brewing time tomorrow too.