[Beijinger]

Why should she not be able to detect some kinds of cancers? Some dogs can.

In the end, all this should not be so difficult. Take the head space, then do MS of a bunch of people with these diseases and the head space and MS of healthy people as a comparison. The delta gives the disease.

[londons_explore]

I'm not sure any of today's mass spectrometers yet can match human smell in sensitivity, at least to some scents with larger more complex molecules.

[Beijinger]

"with larger more complex molecules."

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

[kolinko]

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

[literalAardvark]

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

[Beijinger]

You don't smell proteins.

[throwawaymaths]

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

[londons_explore]

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.

[sseagull]

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.

[throwawaymaths]

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