1) In regards to the xyelene pulls, would I only do this once (as in the four suggested shake/separate cycles as per 'Step Six: Adding the Non-polar Solvent'), or would I do what is requested in 'Step Seven: Pulling', and do the xylene pull another 4 times (essentially 16 shake/separate cycles when all is said and done)?
You can do a couple of extra vinegar washes to ensure that all the DMT gets recovered from the xylene.
Before that, the xylene pulls from the bark soup tend to be a lot more effective than naphtha, therefore you'll likely get away with doing just a couple of them. Xylene's greater solvent ability for DMT is the reason why it can't be used as a solvent for freeze precipitation - it holds onto the DMT too well, even at low temperatures.
2) When adding the pulled xylene into the water/vinegar solution as per 'Step Three: Acidifying', would I need to follow those steps explicitly, namely the heat bath for an hour with the xylene/water/vinegar mixture, or would simply combining them and allowing to separate be adequate?
No heat bath necessary with xylene, for the aforementioned reason. Combine, separate, done.
3) Will pulling the xylene out from the water/vinger mixture be easily achieved, as I imagine there won't be the same contrast in colours that makes the NPS as distinct when working with the original mixture containing the plant matter?
There should still be a visible boundary between the two layers because the have different indices of refraction - i.e., each bends light by a differing amount. This would be an ideal usecase for a separatory funnel, btw. Otherwise, do something to ensure that the boundary layer sits within the confines of as narrow a vessel as possible (e.g. bottle neck), or use the funnel trick, to make pipetting easier.
4) If the salting was undertaken as part of the initial xylene pulls, would it be redundant to salt again as per 'Step Four: Salting', or perhaps I should only salt for the first time, after the xylene has been pulled from the now alkaline laden water/vinegar mixture, and before/during the subsequent basifiying step?
There' a confusion here stemming from "salting" being used as a term to describe two separate things on different occasions. Step 4 refers to the addition of common salt - sodium chloride - to the mixture prior to doing the pulls. This is done in order to increase the ionic strength of the solution, so the non-polar freebase migrates to the NPS more readily. This is not strictly necessary when working with xylene, but it won't hurt.
What is necessary with xylene is that you use an acid to recover the DMT (if you don't want to evaporate a load of incredibly stinky solvent, which is both wasteful and environmentally irresponsible) since, as already mentioned, freeze precipitation won't work. This is also commonly referred to as "salting" since the DMT gets converted back into its protonated "salt" form, and thereby reverts to being water-soluble.
You can, therefore, wholly omit the bit about putting the solvent in the freezer
iff you're using xylene, as you said:
finish the tek as per normal, but using shellite as the final NPS to allow freeze precipitation.
you got this!
[This also highlights to me that the freeze precipitation step (part 6 of step seven) isn't explicitly mentioned in the index structure - maybe I'll remedy that soon.]
And apologies for occasionally stating the obvious - I'm writing as though this information will be more generally applicable.
