You might want to check out the
tobacco extraction sub forum at the top of this forum.
Here's a good
thread from there:
http://www.e-cigarette-forum.com/forum/liquid-extraction-tobacco/99774-vg-pipe-tobacco-essense.html
As I recall, Kurt, who is an esteemed chemist in this community, finds it unlikely that his method would extract any significant amounts of nicotine.
That said, I would also say that other extraction methods could quite possibly extract higher amounts of nicotine, but it would not be likely to be dangerous. Research how much nicotine (in milligrams) is in whatever amount of tobacco that you wish to extract from, and divide that by the amount of liquid yield (in milliliters.) That would be the maximum possible mg/ml that the extract could contain, but it would be unlikely to be anywhere near that much unless you were specifically trying to extract alkaloids, IMO.