With ever stronger magnets coming out every year, LC-NMR coupling becomes more attractive and is now used frequently in the pharmaceutical industry as well. Considering the rapid progress that is made in that direction I wondered why no MS-NMR coupling has been reported yet, especially as gas phase NMR is possible already. So I wondered: When will it be possible to do MS-NMR coupling? What are the biggest obstacles for achieving MS-NMR coupling?
(The magnets are not really getting stronger. The > 20 T magnets are still too big and expensive to be widely used. First 900 MHz was from 2001, the 1GHz Bruker magnet came out five years ago. Since then seemingly nothing... except this 1020 MHz hybrid prototype by JEOL et al. Looks a bit unwieldy. There is a reason it is a hybrid (inner coils made of Bi-2223, i think): The classic superconducting materials (Nb3Sn, NbTi) have an absolute upper limit of ~25 T. HTSC can go higher, but they are very difficult in manufacturing. )
Fundamental problem is T1 relaxation in the gas phase. It is much too slow. You need hyperpolarisation techniques, that you have to interface with the GC. Difficult. (Impossible with mass spectrometry, because there the sample is in vacuum.)
The amount of analyte would be tinytiny. Likely impossibly small for NMR, even with hyperpolarisation. Certainly too small with mass spectrometry.
Other point: Why? GC is not useful for complex molecules, because the have very little vapour pressure. For less complex molecules, GC-MS is fine. There are a number of working NMR techniques to separate different analytes. HPCL-NMR, GPC-NMR, DOSY, etc.
I guess nobody has seen a problem that needs GC-NMR to solve it. Or at least he has not been able to convince anyone it would be worth financing it.
(I initially misread the original question to be about a GC-NMR combination. Hence all the GC in my answer.)