Disclosed is a pre-treated ion exchange resin comprising at least 15% by total number of exchangeable groups comprising at least one of an ion, or a Lewis acid, or a Lewis base resulting from a heat transfer fluid component having a pK.sub.a or pK.sub.b of greater than 5 in an aqueous solution at 25.degree. C., based on the total number of exchangeable groups. In one embodiment, the heat transfer fluid component is at least one of a colorant, a corrosion inhibitor, an antifoaming agent, a bitterant, a dispersant, or a combination thereof. In one embodiment, the heat transfer fluid component comprises a heat transfer fluid corrosion inhibitor. Also disclosed are heat transfer systems, assemblies, fuel cell systems and methods of maintaining a conductivity of less than 200 .mu.S/cm in a heat transfer fluid that employ the disclosed pre-treated ion exchange resins.