Hi Jan !
A word of caution : I used Protectan on E6 chemistry concentrate (Kodak) and it appears it has turned the chemistry bad on the colour developer.
I suspect the butane has reacted somewhat with one of the compound of the chemistry.
I a very old book of darkroom practice, I've seen a drawing for a can devised to hold chemistry unaffected for long periods : the bottle has a pump to get it pressurized, and a tube to collect the chemistry from the bottom. Once partially filled, you deposit a thin coating of oil on the chemistry making an air barrier ..... Avoid using the last cc of chemistry if you do not like oily negs ;-)