STUDY OF THE THERMODYNAMIC BEHAVIOR OF RARE-EARTHS IN THE SYSTEM OF R-SO3H-ALPHA-HIBA ON HPLC AND ITS APPLICATION TO ANALYTICAL-CHEMISTRY

The thermodynamic behavior of rare earth elements in the system of R-S O3H-alpha-hydroxyisobutyric acid on HPLC has been discussed. The stand ard enthalpy change Delta H-REE(o), the related standard free energy D elta G(REE2,REE1)(o), and the related standard entropy Delta S-REE2,RE E1(o) in the system have been calculated and explain the separation re gularity of rare earth elements in this system. Rare earth elements ca n be satisfactorily separated by gradient elution of pH with alpha-HIB A as mobile phase and Zipax SCX cation exchange resin (R-SO3H) as stat ionary phase. The content of rare earth element in the effluent is det ermined with postcolumn derivatization Arsenate III spectrophotometric analysis. This method has been applied to the analysis of a synthetic sample and a geological standard sample GSD-2 from China. The related standard deviation of six duplicate experiments is less than 5% for a ll rare earth elements. (C) 1995 Academic Press, Inc.