I am making a stock solution of Tween 80 (0.05 % w/v) and each experiment requires just 15 ml of the stock solution. Is it possible to make a large batch (about 100 ml) and store it somewhere? If so, what should I look out for when storage?
The Sigma Aldrich/Merck product information for "TWEEN® 80 solution" states the following:
Aqueous solutions of polysorbates as well as the neat liquid will undergo autoxidation over time, with changes being catalyzed by light, increased temperature, and copper sulfate.
Solutions are reasonably stable at 2 - 8 °C for short periods. For special applications, storage under argon or nitrogen may be preferred.
[9.] Donbrow, M., et al., Autoxidation of polysorbates. J. Pharm. Sci., 67, 1676-1681 (1978).
While this is not a very specific time span, it clearly indicates that TWEEN solutions are not long-term stable. If you need to store it, then in a fridge, protected from light and preferentially under an inert atmosphere for a few days max.