2007 InternationLast saved by CRal Nuclear Atlantic Conference - INAC 2007 Santos, SP, Brazil, September 30 to October 5, 2007 ASSOCIAÇÃO BRASILEIRA DE ENERGIA NUCLEAR - ABEN ISBN: 978-85-99141-02-1 INAC 2007, Santos, SP, Brazil. 1 POLAROGRAPHIC DETERMINATION OF Sn (II) AND TOTAL Sn IN PYRO AND MDP RADIOPHARMACEUTICAL KITS Maria V. A. Sebastian 1 , Marcelo Di M. V. Lugon 1 , José L. da Silva 1 , Neuza T. O. Fukumori 1 , Nilda P. S. de Pereira 1 , Constancia P. G. da Silva 1 and Margareth M. N. Matsuda 1 1 Instituto de Pesquisas Energéticas e Nucleares (IPEN/CNEN-SP) Av. Professor Lineu Prestes, 2242 – CEP 05508-000 - São Paulo, SP marcelolugon@terra.com.br ABSTRACT A sensitive, alternative method to atom absorption spectometry, fluorimetry or potentiometry for the evaluation of tin(II) ions (0.1- 10mg) and total tin in radiopharmaceutical kits was investigated. Differential pulse polarography was chosen. The supporting electrolyte was H 2 SO 4 3 mol L -1 and HCl 3 mol L -1 solution. The potential was swept from –250 to –800 mV vs Ag/AgCl/saturated KCl, using a dropping mercury electrode with 1 s drop time, 50 mV s -1 scan rate, –50 mV pulse amplitude, 40 ms pulse time and 10 mV step aplitude. Pure nitrogen was used to deaerate the polarographic cell solution for 5 min, before and after each sample introduction. Oxidation of Sn(II) was made in the same sample vial by adding H 2 O 2 (hydrogen peroxide) 10mol L -1 , at 37°C, in order to quantify the total Sn. The calibration curve for Sn(II) and Sn(IV) was obtained in the concentration range of 0-10 ppm from a 1000 ppm standard solution. The detection limit of Sn(II) is 0.5ppm and for Sn(IV) is 0.6ppm. Differential pulse polarography was performed in the pyrophosphate (PYRO) and methylenediphosphonic acid (MDP) radiopharmaceutical kits, containing 2 mg and 1 mg of SnCl 2 .2H 2 O per vial, respectively. The described method for determination of stannous ion (Sn(II)), is selective, reproducible and adequate to be used in the quality control of lyophilized reagents and it shall be performed for other cold kits produced at IPEN. 1. INTRODUCTION Stannous chloride is the major compound used for reduction of generator-derived 99m Tc- pertechnetate in cold kits for on site preparation of 99m Tc-radiopharmaceuticals. These cold kits usually contain a ligand, stannous chloride (SnCl 2 .2H 2 O), and different additives (complexing agents, antioxidants, buffers, etc.). The amount of stannous ions Sn(II) varies from kit to kit. In technetium labeling kits, where SnCl 2 .2H 2 O is used for stabilizing the system, it is important to know the exact concentration of Sn(II) for 99m Tc-pertechnetate reduction and the concentration of total Sn considering toxicological effects [1]. Various techniques were described for tin determination (atom absorption spectometry [2], titrimetric methods [3], spectrophotometry of tin complexes [4] or chromatography [5]), but they cannot distinguish between stannous (II) and stannic (IV) ions in solutions. Titrimetric methods, which are selective for Sn(II), are generally less sensitive. Nevertheless, with appropriate amounts of Sn(II) (0.1–10mg), the titration is not a time consuming method. Colorimetric methods are often associated with problems of specificity and stability of the formed tin complexes. The two methods described in literature for selective determination of Sn(II) are polarography and mass analysis (redox-titration). Polarography is a good selective method in the mg range as well as in the μg range for Sn(II) and Sn(IV) [6].