media query and not

media query and not

I have the following less code:
@mobile: ~'screen and (max-width: 480px)';
Then I use it as follows:
@media @mobile {
// some code
}
It works fine but I would like to also use "not" like:
@media not @mobile {
// some code
}
But I get the error "ParseError: Unrecognised input" in the "not" part.
Is it possible to solve this?
Thank You, Miguel