Coming across this thread in my "perfect" gin & tonic research, while not using bark or syrup, I decided I may as well report in with my results.
I decided to see how easy/hard it was just to get quinine sulfate and start from there. The reason was ultimately a desire to have better control over the finsihed product. I actually found several viable sources for USP grade chemical, but several required some proof of academic affiliation, i.e I would either have to work/teach at an actual educational instituion or lie. In the end, I found two soruces that would ship small quanitites of quinine sulfate - The Lab Depot (www.labdepotinc.com) and ArtChemicals (artchemicals.com). The latter will ship out of the US, while the former will not.
Past that point, I followed some of the guidelines around process provided by Dave Arnold (Thanks Dave!) in one of the Harvard lectures and ran some taste experiments. After some spirit-fueled debate, the recipe that scored the highest was more or less the following:
60 ml Gin
25 ml Clarified Lime Juice
15 ml Simple Syrup
100 ml water
3 ml of 0.2 % Quinine solution
Pinch of salt
Mix the above and chill in Freezer. Add to ISI (optionally with ice), shake and carbonate with two CO2 and one N2O charge. Serve and enjoy slowly. Nice balance of taste that gets even better as you go and bubbles that last right to the end. I should say that this results in a very stiff drink, so I'm not sure more than one would be required, but your mileage may vary.
Edited by Bohemian, 18 September 2012 - 04:54 PM.