Best practices to obtain small quantity of sealed solution without oxidising entire solution?

I'm ordering liquid based chemicals which only come in large bulk quantities. These solutions have a shelf life of approximately 2 years unopened, but 2 - 3 weeks once opened and oxidation kicks in. To put things into perspective, they come in 5 litre bottles to dilute to 50 litres but I only require 100ml per use. So going through 5 litres in 2 - 3 weeks is not realistic whatsoever.


So this got me thinking if there is a way I could obtain small quantities of a solution without at all exposing the entire solution to the atmosphere? The first thing that comes to mind is to obtain the solution within a vacuum chamber, then finding a way to vacuum seal the bottle back up.


Would that be a good practice or are there better ways to work around this problem?


