Purify the salt on a phosphocellulose column and elute with a gradient of aqueous NH3 (0-10%). The second major peak has the characteristic tryptamine spectrum and is collected, and lyophilised to give white crystals of the dihydrate which dehydrates at 100o. It has UV max at 274.5nm ( 1,310) in 0.1N NaOH and 274.5nm ( 1,330) at pH 7.0. Excitation max is at 280nm and emission max is at 330nm. [Mekalanos et al. J Biol Chem 254 5849 1979.]
