Just to be sure...
When I see some natural gas mixtures mostly its broken down into volume percent but every once in a while i see mole percent. Its my understanding that these values (%mole and %volume) are the same. Am I correct?
Because your assumption here is Ideal gas conditions. PV=nRT so your V% should go along with the n% as long as your not close to the critical point or phase changes as previously point out.
So as a rule you can't apply this on liquid chromatograph readings. Adding Compressibility factors can help you get closer to those vol% to mol% conversions.
Awesome reference paper Ione; I will forward this to all everyone here.