I intend on making caffeinated water for personal consumption, in batches large enough that it will take several months to consume them, using containers which are not hermetically sealed, and for which it is not practicable to refrigerate. What would my options be as far as preservatives?
Commercial caffeinated water products i've bought use sodium benzoate, but I can't seem to find information on how much to use. I am also interested in the possibility of using citric acid, but again i'm not sure what pH level I would be looking for. If it matters I do have a lab grade balance (Sartorius Entris 64-1S) which would be capable of measuring sub-milligram amounts and a dispenser to match.