Purifying WTA down to just nicotine is like the mistake of purifying wholewhat down to white flour. It's enough to remove the storks.
With vitamins and minerals there are balances for ideal efficacy. B-vits best taken as a group, calcium with magnesium and potassium (and D), E should be the E-family not just the alpha tocpherol, ... I think nicotine w/o the other alkaloids is a bit like this.
Nicotine historically always had been used in WTA form, after all. What is untested is using nicotine on its own long-term.