Good morning Annie and community!
I am currently using hexane as my workhorse extraction solvent.
I would like to try butane or propane (yup, Vietnamese soup lol) as the extractant, as I think that either in a closed system will return better selectivity over hexane or anything else i can keep in an unpressurized bottle.
Where I gain confidence that any and all solvent is removed from the products Annie has shown above is that I do something apparently unique in the biz.
I distil the extract under a high vacuum.
This leaves the fixed contaminants and most pigments behind. It also comprehensively decarboxylates the THCA, CBDA etc. without opportunity for oxidative loss. Finally, it makes for a complete vacuum purge of all volatiles, including (alas) the flavor monoterpenes.
I am working to the point where I have built an independent capacity to not only purify but assay these distillates for content of THC. The bonus is that I will have some water-white 99+% delta-nine THC as both an analytical sample and a trial medicine for patients who have especial tolerance combined with especial sensitivity. Annie and I are laying the foundations for a project to deliver these refined materials effectively as an oral preparation.