Here is what I do to keep my powders "pure". Against the recommendations of the powder manufacturers, I never pour powder back in a bottle once I pour it out. For some reason, my mind sees pouring powder in a hopper, then back into a bottle after using that hopper for other powders as cross contamination. I have always stored powder that was in a hopper in a separate container. I use the ziplock type bowls labeled with the specific powder. I also leave the bowl for the powder in use on my work bench until I am done with that powder that way I know what powder is in the hopper. This also prevents me from ruining a whole factory bottle because I dumped the wrong powder back in on top of it. If I mix them up, it is in a smaller container with less powder to ruin.

Rosewood