Yes, I think you can. In the same way that you can use different things like hair or a doll of a piece of clothing as an item of concern your cotton is probably a symbol instead of an essential magical item. Which spell is it?
Which spell are you referring to? Do you have the link? It could be a symbolic thing so you might not need a particular kind. But the context of the spell could be important and it might need to be a specific kind for a specific reason. But without seeing the formula of the rest of the spell and the theme they were going for, it's hard to tell.