Synergistic effect of temperature and background counterions on ion-exchange equilibria.

The effects of temperature and background counterions on ion-exchange selectivity for alkali metal ions and tetraalkylammonium ions on strongly acidic cation-exchange resins have been investigated using superheated water ion-exchange chromatography (SW-IEC). We have found out that alkali metal ions show reversal in the order of the distribution coefficient ( ), from Li < Na < K < Rb in water at ordinary temperature to Rb < K < Na < Li in superheated water, when a relatively large cation such as cesium ion is used as the background counterion. The effect of counterion on the ion-exchange selectivity is enhanced with the ion-exchange resins of higher ion-exchange capacity and cross-linking degree.

H and C NMR spectra of 4,4'-substituted chalcones.

H and C NMR spectra of chalcone (trans-benzylideneacetophenone) and 54 4,4'-substituted chalcones were studied. The 400 MHz H NMR and the C NMR spectra were observed, analysed and assigned and the substituent constants were calculated by the least-squares method.