Efficient Chromatographic Evaluation of Crown-Ether Complexation with Alkali-Metal Ions

2016

Chem. Rec.

Ice has a variety of scientifically interesting features, some of which have not been reasonably interpreted despite substantial efforts by researchers. Most chemical studies of ice have focused on the elucidation of its physicochemical nature and its roles in the natural environment. Ice often contains impurities, such as salts, and in such cases, a liquid phase coexists with solid ice over a wide temperature range. This impure ice also acts as a cryoreactor, governing the circulation of chemical species of environmental importance. Reactions and phenomena occurring in this liquid phase show features different from those seen in normal bulk aqueous solutions. In the present account, we discuss the chemical characteristics of the liquid phase that develops in a frozen aqueous phase and show how novel analytical systems can be designed based on he features of the liquid phase which are predictable in some cases but unpredictable in others.

Section: Reactions In the Liquid Phasementioning

confidence: 99%

Micro- and Nano-Liquid Phases Coexistent with Ice as Separation and Reaction Media.

2016

Chem. Rec.

“…In the cation-exchange method, we used mixed-bed stationary phases (mixtures of active and inactive stationary phases) to reduce the total capacity of the resin. 13 A disadvantage of this strategy is a requirement of column repacking. In contrast, the surface charge density as well as the total capacity can be varied in the anion-exchange method by a simple procedure, i.e.…”

Section: Precision Of Complex Formation Constantsmentioning

confidence: 99%

“…A number of tools, including calorimetry 1,2 , conductometry 3 , potentiometry 4 , and spectrometry 5,6 , have been developed, and successfully employed. We have shown that some separation methods, such as chromatography 13,14 and electrophoresis 15 , are suitable for the determination of polyether complexation constants in solution, and have elucidated some aspects in polyether chemistry, which have not been understood because of the lack of effective approaches. 14,16 These developed methods have some advantages over other conventional tools; i.e.…”

mentioning

confidence: 99%

Secondary Equilibrium Chromatographic Evaluation of Polyether Complexation Using an Anion-Exchange Resin

Quraishi

1999

ANAL. SCI.

Secondary equilibrium chromatography has proved a useful tool for determining the polyether complexation constants. Both a cation-exchange and anion-exchange method can be used for this purpose. In the present paper, the applicability and versatility of the latter method, based on the surface complexation of polyethers with ammonium ions anchored on the stationary phase surface, are discussed, and compared with those of the former established method. The precision of the chromatographically determined complexation constants depends on the range of measured retention factors, suggesting that the surface charge density of the stationary phase can be optimized according to the retention ability of polyethers. The anion-exchange method is more versatile than the cation-exchange method from this viewpoint; i.e. the surface density of active groups (thus the retention range) can simply be controlled by preequilibrating the stationary phase with an aqueous solution of appropriate pH.

“…65 In the separation sciences, polyethers have been mainly used for the separation of cations, while very little attention has been paid to the separation of polyethers themselves. It has been reported that the chromatographic separation of polyethers provides very useful information on the solution behaviors of polyethers [66][67][68][69][70] , which cannot be elucidated by other methods.…”

Section: ·4 Polyether Complexation At the Surface Of Ion-exchange Rementioning

confidence: 99%

Interpretation of Chromatographic Retention Based on Electrostatic Theories

1998

ANAL. SCI.

Electrostatic potential is responsible for various phenomena, particularly for the behaviors of ionic species in solution and at various interfaces. In some modes of chromatography, electrostatic interaction often governs overall retention selectivity; ion-exchange chromatography is a typical example. Thus, though the understanding of electrostatic interaction is essential to interpret and predict chromatographic retention in some cases, sufficient attention has not been paid to its roles. There are some possible reasons for this situation: (1) direct estimation of the potential is usually difficult; (2) simple models not involving the contribution from electrostatic potential have given rather good explanations to experimental data. Some research groups have recently attempted to take electrostatic potential effects into consideration in various ways, and have successfully developed chromatographic models. These approaches are expected to facilitate understanding of chromatographic phenomena dominantly controlled by electrostatic interaction and to provide a view of more physical significance. In this review, the author mentions advantages of chromatographic models based on electrostatic theory over usual separated-phase models, and shows problems to be solved.