STDS STUDY FOR THE IDENTIFICATION OF RELEASED COMPOUNDS FROM COMMERCIAL ION-EXCHANGE RESINS

Physical and chemical stability of polymeric sorbents, including ion-e xchange resins, is among the main concerns of both manufacturers and u sers. Different countries are gradually introducing regulations for th e use of ion exchangers in water conditioning, food and beverage proce ssing, separation of pharmaceutical products, and also for the use of reference materials as drugs and medical devices. Since all the applic ations mentioned may directly influence human health, the treated prod ucts must be free of any trace toxic compound potentially released by the polymeric matrix of the sorbent. The System for Thermal Diagnostic Studies (STDS) has recently been introduced commercially as a new ver satile and powerful technique for the identification of the products e volved after thermal stress of solid phases. In this paper are present ed the results of an STDS investigation to simulate the release of org anic compounds from commercial weak and strong electrolyte anion and c ation resins, differing for the type of polymeric matrix (polystyrene and polyacrylic based), porosity (gel and macroporous type), and funct ional groups, including sulfonic and carboxylate functionalities for t he cation resins, and secondary, tertiary amine and quaternary ammoniu m functionalities for the anion resins. STDS determinations were carri ed out at 130, 200, 250 and 300 degrees C by using a constant reaction time (10 min) and an inert (He) gas atmosphere. The thermally release d compounds were cryofocused at -60 degrees C and separated by tempera ture-programmed gas chromatography. The qualitative identification of the released compounds was made by searching the MS library NBS 54K. T hermogravimetric determinations were also carried out on a set of cati on resins to complement STDS data.