Rustica is also a known producer of TSNAs (Tobacco-specific nitrosamines). This means that you'll be extracting the cancer-causing aspect (which are also 'WTA'; ie; N-nitrosonornicotine, 4-methyl-N-nitrosamino-1-(3-pyridyl)-1-butanone, N-nitrosoanatabine, & N-nitrosoanabasine) of this tobacco alongside the desired alkaloids.
It's 5% no matter the strength (unless separate nicotine is added in). The minor alkaloids would be 5% (an approximation) whether it's pure, 50 mg, 25 mg, or 5 mg. WTA is 95% nic and 5% minor alkaloids (roughly).
From what (little) I know (and in agreement with snork), alkaloid content may vary by strain of tobacco. This is why it's so important to research the specific tobacco one plans to use in such an extraction. That said, at least it's not the pyrolysis byproduct of nicotine, which is rather carcinogenic in and of itself.
Akin to WTA content, TSNA content can vary just as wildly depending on whether you're looking at a producer or non-producer (tobacco strain) of TSNAs.
Just make sure to research the certain type of tobacco you're using, make sure it isn't a known producer of TSNAs, or you're going to concentrate the harmful ones alongside the desired ones.
I advise everyone considering contracting someone to do such lab work to do the same.
Suffice it to say that research is
required in this endeavor.
That's all for now!