With respect to Graduat school application, GPA is always the most they emphasize, no matter if you have graduate degree or not, if your GPA is not very impressive, the only thing you can do is to get a good Sub score to make it up to some extent.
In Chemistry departments where committees make the final decision, your research experience doesn't count that much. I knew that a guy who has a master degree from NUS, working with a very well-known professor in chemical biology, publishing 4 first author paper (2 Org Lett and 2 Chem Com) got zero offer for the application.
So trust me, the only thing you need to do is to get a good GRE sub and IBT speaking, both of which are way more important than your reserach experience. Remember you are applying to do graduate studies, not postdoc position and faculty position.