RESUMO
Ionization constants for acid functions of D-penicillamine, L-cysteine, thiomalic acid, and thioglucose were measured by pH titration at 37 degrees and 0.15 M ionic strength. Chelate formation constants for these ligands with calcium(II), iron(III), and gold(I) were then determined under the same conditions chosen to approximate the in vivo situation. Only iron(III) formed both 1:1 and 1:2 chelates with D-penicillamine, L-cysteine, and thiomalate; calcium formed weak and gold strong 1:1 complexes with all ligands studied. Because of precipitate formation, the stability constants for the systems thioglucose-iron(III), D-penicillamine-gold(I), and L-cysteine-gold(I) had to be determined indirectly with thiomalic acid as the competing ligand. The in vivo fate of antiarthritic gold(I) compounds remained uncertain, but gold(I) chelates probably persist as such for extended periods.
Assuntos
Cisteína , Ouro , Compostos Organometálicos , Penicilamina , Ácidos , Quelantes , Fenômenos Químicos , Química , PotenciometriaRESUMO
Cation-exchange chromatography in a dimethylsulphoxide (DMSO) medium is a suitable means for separating uranium from metal ions, including copper, iron, nickel and molybdenum. Quantitative separations of uranium from 26 elements can best be effected on a column of Dowex 50W-X8 (200-400 mesh), using as the eluent a 20% v/v DMSO solution which is 0.6Min hydrochloric acid and 0.25M in sodium acetate. Only calcium is eluted with the uranium and all other elements studied are eluted either before or after uranium. The elution characteristics of uranium and of other metal ions were investigated with respect to changes in eluent and resin compositions. Separations were much less effective at higher concentrations of sodium ion or DMSO. None of the organic solvents methanol, ethanol, methyl glycol, acetone, dioxan or acetic acid was found to produce favourable separation conditions. Results with Dowex 50 resins of lower or higher cross-linkage were inferior to those obtained with the X8 resin.