You need to prepare a solution of 1 part 5%vinegar 7 parts water, heat that solution then add it slowly to the powder, only the harmalas should dissolve, when nothing seems to be dissolving anymore, wait for the impurities to settle then filter the solution

The filtered liquid contains the harmalas,you need need to basify it now by adding lye or sodium carbonate, if the solution turns cloudy then there is harmalas if not then there isn't..

EL but You can make a 10x caapi leaf and use it to make changa

Edit: Sorry i got confused between steps, no need to use vinegar, just hot water but it's not a problem if you already used it.