It has just dawned on me that since citric acid and DMT citrate are soluble in acetone, shouldn't the same go for sodium citrate? If so, if one were to do an acetone pull on an evaporated solution of alkaloids that had been initially extracted in a citric acid solution, which was then based with sodium carbonate, there would be contamination problems, no? If this is the case, would using freezing-temp acetone be viable for picking up alkaloids but minimising this contam?

That's one line of reasoning but it won't necessarily be valid.

I don't have any figures to hand (without searching the internet) so I'll stick with this suggestion - it's likely to be equally as important to use dry (anhydrous) acetone if you want to minimise the solubility of sodium citrate in said solvent.

Drying acetone is notoriously difficult, since it undergoes aldol condensation with itself and always exists in equilibrium with some diacetone alcohol and water.

The best drying agent for acetone is boric anhydride (boron trioxide), but it is somewhat hard to find and tricky to make as it involves heating boric acid above 350°C. The second best option is 3Å molecular sieves for no longer than 6 hours followed by their removal.

I would simply rinse the final product with a bit of freezer-cold concentrated ammonia - it will remove any water-soluble impurities (such as sodium acetate) that did not co-crystallize with DMT, and evaporate cleanly.