Application of cation-sensitive glass electrodes to the study of alkali metal complexes—II1Use of a potential comparison method

Equilibria and Dynamics of Sodium Citrate Aqueous Solutions: The Hydration of Citrate and Formation of the Na3Cit0 Ion Aggregate

“…Our results appear to contradict previous publications, ,− which did not find the formation of Na 3 Cit 0 but partly claimed the existence of Na 2 Cit – . − On the other hand, both species appear in the MD simulations of Wright et al, who reported relative species concentrations of 15.2% free Cit 3– , 44.5% NaCit 2– , 35.2% Na 2 Cit – , and 4.9% Na 3 Cit 0 at [Na 3 Cit] T ≈ 0.06 M.…”

“…This difference can be rationalized by the law of mass action: due to the proportionalities [Na 2 Cit – ] ∝ [Na + ] T 2 ·[Cit 3– ] T and [Na 3 Cit – ] ∝ [Na + ] T 3 ·[Cit 3– ] T , the formation of Na 2 Cit – is favorable at the low concentrations investigated in previous studies, ,− whereas that of Na 3 Cit 0 is preferred in more concentrated solutions such as those the present work. Consequently, the detectability of the 2:1 and 3:1 species heavily depends on the applied concentration range.…”

“…Based on literature results, ,− we first assume the formation of the NaCit 2– and/or the Na 2 Cit – species. Considering only the 1:1 ion-pair, we observe that the fitted curves deviate significantly from the measured ones (blue curves in Figure ).…”

“…By way of example, the strong interaction between Cit 3– and Ca 2+ ions − is essential for the stabilization of apatite nanocrystals in bones . As for Na + , the Coulombic attraction between Cit 3– and the cation is considered in the literature to be rather weak, explaining the low stability of the NaCit 2– ion-pair. ,− Nevertheless, the binding of a second Na + i.e., the formation of the Na 2 Cit – ion aggregatewas also detected in dilute solutions. − (In the present work, the species containing only one cation is termed as an ion-pair, while higher-order associates are referred to as ion aggregates.) It is also of interest that the uptake of extracellular citrate in mammals takes place via sodium-coupled citrate transporters, , which may be linked to ion association between Na + and Cit 3– , highlighting its biological relevance.…”

Komplexe von Enniatinen und anderen Antibiotica mit Alkalimetall‐Ionen

“…Experimentelles. -Die Ill.-Absorptioizsspektren wurden mit einem PERKIN-ELMER-SpCktrODie Kovnplexbildungskonstanten wurden im wesentlichen nach veroffentlichtem Verfahren [14] photometer Modell 125 aufgenommcn.…”