I agree; but if the key thing is to
tell the difference between the homeopathic preparation and the stock solvent, and you want to do that by, say, radiotracing as geni suggests, to establish the presence of a molecule contained in one sample which is not in the other -
that, presumably, would be
acceptable (as Mojo points out on the thread Rolfe linked to), right?
Assuming the procedure had been correctly carried out to start with.
So in actual fact, the presence or non-presence of various molecules could be very important, if telling the difference between the two 'preparations' is acceptable.
I don't think analyzing for a few molecules is a viable approach at all.
I'll surely regret this, because I'll probably soon see one of these goons claiming that "MRC_Hans has admitted that there are molecules in all potencies", but:
We are talking about Avogadro's number and "no molecules", but all that is mainly an academic exercise. In the real world, it would require ridiculously strict lab procedures to actually produce a sample that did not contain even a single molecule of any substance that has been present in the lab. In fact, I doubt if it can be done.
In any lab, here will be a "noise floor", dependent on the quality of the lab procedures, and below that, you are likely to find loose molecules of any substance that was ever present in the lab, in any sample.
I have seen pictures of a Pakistani homeopathic laboratory. It was an ordinary room in an ordinary building, with a wooden floor, painted walls, and several ordinary doors and windows. The laboratory benches were wooden tables, of the dinner-table type, and on them were a few devices resembling the machine MAS posted a picture of. The picture did not show, but I strongly suspect that their remedies, mother tinctures, dilution medium, and empty vials sit on open shelves somewhere in that, or another, room. In such a setting, I'd estimate the noise floor, or contamination floor, is at several ppm. So at 3C and upwards, their products will more or less be a conglomerate of whatever substance happens to be present in the building at the time.
You see, this is another incongruency of homeopathy, albeit one that is rarely mentioned: The laboratory practices required to produce even medium potencies (no matter whether they are possible or not) which are consistent and clean, would be totally absurd. If you were to convince the FDA that your Bel 12C is indeed unadulterated medium with a single belladonna molecule in it, you would need to have a clean-room setup that would make a semiconductor lab look like a sweat-shop.
And don't get me started on 200C

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Hans