Preparation and Analysis of 4-Iodoantipyrine-(I-131)

4-lodoantipyrine was prepared from antipyrine according to the reaction equation: 3C(11)H(12)N(2)O + 2KI + KIO3 + 3HCl -> 3C(11)H(11)N(2)OI + 3KCl + 3H(2)O The product was separated from the reaction mixture and purified by recrystallization. The iodoantipyrine was labeled with I-181 by means of an exchange reaction with NaI181. It was separated from the unbound radioactivity by anion exchange chromatography. The purity of the product was determined by cellulose thin layer chromatography using ethanol-chloroform-water (45:45:10) as the solvent system. The purity of the 4-iodoantipyrine-I-181 decreased with time due to a splitting off of the Ps' atom and subsequent formation of NaI181, This spontaneous deiodinaiion was best minimized by storage in methanol at low temperatures.