I recently did a water quality test and it showed a detectable level of perfluorobutanoic acid, a potentially dangerous carboxylate PFC.
Will a reverse osmosis water purification system exclude this chemical?
It will depend on the membrane used for reverse osmosis and what your goals are. Are you trying to completely remove the acid or bring it down to an acceptable level?
The study here states that
...reverse osmosis (RO) treatment technologies have the ability to effectively reduce perfluorochemicals (PFCs) in water...
The take away is that it may not eliminate the perfluorobutanoic acid completely, but may reduce it to a safe drinking level.
All RO devices removed PFCs to below testing reporting limits of 0.2 µg/L.
The next sentence is probably what you're really after.
The effectiveness of RO devices is due, in part, to these devices having both AC and RO components.
So you may want to look into a system that offers more than just RO. This article summarizes some research that was done on RO effectiveness for removing perfluorobutanoic acid which may be of some use for you.
At the end of the day, I would suggest talking with sales representatives of specific RO devices. Tell them what you're after and they should be able to recommend a product for you.