Preparations of meta-iodobenzylguanidine and precursors thereof

A method for preparing a purified composition of a polymer comprising a monomer of formula (I):

• or a pharmaceutically acceptable salt thereof,
• the method comprising the steps of:
• counter ion exchange of a hydrochloric acid form of the monomer of formula (I) with sodium acetate to thereby provide a preparation comprising the monomer of formula (I) in the form of a HOAc salt;
• a first solvent treating step, comprising contacting the preparation with aqueous alcohol, and then removing substantially all of the aqueous alcohol;
• a second solvent treating step, comprising contacting preparation with anhydrous alcohol, and then removing substantially all of the anhydrous alcohol so that a solvent-depleted material comprising the polymer is generated;
• and
• subjecting the solvent-depleted material to vacuum, and to a temperature within a range of about 30° C. to about 50° C., the subjecting being performed under conditions and for a time sufficient to thereby provide the purified composition of the polymer, or pharmaceutically acceptable salt thereof;
• wherein no more than 150 ppm of leachable tin is present in the purified composition of the polymer.