"with larger more complex molecules."

What are "larger, more complex, molecules"? Without trolling, I think scent cuts off at a MW 330 or something.

But it's not as good with distinguishing complex organic molecules one from another, no? I.e. between various proteins of a similar size.

Mass spectrometry gives results that are a bit like the ingredient lists for food. Tells you precious little about the actual product.

You don't smell proteins.

Mass specs can detect down to the ten thousands? IIRC or so molecules.

But I don't think they can do that at the same time as having trillions of some other uninteresting molecule like water in them.

It's basically a dynamic range problem.

Mass specs would have this problem, yes. That's why they are usually paired with chromatography of some sort (usually GC/MS or LC/MS). The GC or LC more or less reduce a mixture into components, which are fed into the mass spectrometer to analyze what those components are.

Yep the Ms that does this is tethered to chromatography first (sometimes even 2 or 3 different separation schemes in tandem)