Err... hi.
Doesn't the '-ine' in 'nicotine' indicate that it's an alkaloid? Wouldn't A/B be the best way to go, with the proper safety measures (i.e. treat the shit kinda like LSD, don't spill 500ml of supersaturated nicotine solution on yourself)?
If I remember correctly, nicotine oxidizes readily into a brownish liquid, reminiscent of, well, a nicotine stain... if you wish to avoid this, you might want to -store- it like LSD, too.
Last I checked, the average cigarette yielded about 1mg via standard analysis, when smoked... so 1/4 cigarette would be about 250 mics... yeah, micrograms...
I've actually been looking into this a bit myself - I'm more of a junkie than you describe yourself to be. The tobacco companies usually convert it to its free base anyways, just so you know the starting place... make 1 drop = 250 mics, (or for me, about 1-2 mg), keep away from heat, light, and oxygen (isn't it ironic that 'party stores' sell helium?), drop it in a base/oil pipe (often called by the horribly uneducated 'crackpipes' or 'crankpipes' - there's SO much more out there in this world than just one or two things...)
Try not to kill yourself. Most of the rush is the nicotinic dopaminergenic response - prefrontal cortex, I think... there's a nice sedation from the beta-2 nicotinic acetylcholergens - nicotine and cytisine share nearly the same mode of operation, here... check out a crystallized broom, sometime, if you want to see it without dopamine.
Peace.
Rev. Psi Locybe, insane alchemist.