Beilstein says that it can be done in diphenyl ether to 63% yields. It simply said tryptophan was heated for 10 hours in diphenyl ether(I would assume under reflux). Maybe if they refluxed longer yields would have been higher??????
With the above reaction one can seperate the two recover the tryptophan and do it again seperate recover and do it again etc....{The point is that the use of a ketone was not used so it isn't always needed aparently} Polyethylene glycol is a polyether with alcoholic ends. Might work, might not. CHeck er, out!
With a simple column you should be able to seperate these two quite easily(tryptophan from tryptamine). I also did not find much on the use of ethylacetate to do the seperation. That could prove to be quite useful also. On one hand the decarboxylated product could be much more soluble in the EtOAc than the carboxylated precurser.
Diphenyl ether has a very electron poor Oxygen linkage though which could be better than a glycolic polyether in this reaction.
Sorry best I can do!
Post 211603 (https://www.thevespiary.org/talk/index.php?topic=13266.msg21160300#msg21160300)
(Rhodium: "Another tryptophan decarboxylation", Tryptamine Chemistry)