Iodometric determination of gold and platinum by 168- and 126-fold chemical amplification reactions

A simple, low cost method is described for the determination of gold(I) and platinum(II) at the μg level with 8- and 6-fold amplification, respectively. The method is based on oxidation in a solution (pH 2.4–4.3) of gold(I) or platinum(II) with aqueous potassium periodate, masking the unreacted periodate with molybdate and iodometric determination of the produced iodate and gold(III) or platinum(IV). The sensitivity of the proposed method can be enhanced by separation of the liberated iodine on a polyurethane foam column, and oxidizing the collected iodine with an excess of periodate. The iodate produced in the effluent and washing solution is then titrated iodometrically after masking the excess periodate. This procedure offers a 168- and 126-fold amplification for gold(I) and platinum(II), respectively. Analysis of the binary mixtures of gold(I) and (III) or platinum(II) and (IV) in aqueous solution has been carried out successfully.