Solvent Strength Parameters and Retention Factors in Pure Water Using UNIFAC-Predicted Activity Coefficients

2003 ◽  
Vol 42 (25) ◽  
pp. 6320-6330 ◽  
Author(s):  
Jung Hag Park ◽  
Jung ◽  
Mark F. Vitha ◽  
Peter W. Carr
Keyword(s):  
Activity Coefficients ◽  
Pure Water ◽  
Strength Parameters ◽  
Retention Factors ◽  
Solvent Strength

scholarly journals Influence of the composition of the stationary and mobile phase on the retention factors and solvent strength parameters in RP chromatographic systems in which the Everett equation is valid

2001 ◽  
Vol 66 (10) ◽  
pp. 671-683 ◽  
Author(s):  
T.J. Janjic ◽  
G. Vuckovic ◽  
M.B. Celap
Keyword(s):  
Phase Equilibrium ◽  
Equilibrium Constant ◽  
Mole Fraction ◽  
Linear Dependence ◽  
Mobile Phase ◽  
Strength Parameters ◽  
Retention Factors ◽  
Mobile Phases ◽  
Solvent Strength

It is shown how in RP chromatography the Everett equation for ideal phase equilibriums can be used to estimate SP values (SP = log xs/x1, xs and x1 denoting the modifier mole fractions in the stationary and mobile phases, respectively) which are in a linear dependence with the log k values. The described procedure includes the determination of the approximate phase equilibrium constant K. By analysis of the Everett equation it was found that in the field of x1/K there are regions of linear dependence of the SP parameter or log k values and the mole fraction of modifiers or its logarithm. Consequently, only in these regions it is possible for two different chromatographic systems to have the same solvent strength scale: x1 or log x1.

Solubility in the System (NH4)2S2O8—NH3—H2O and Mean Activity Coefficients of Saturated Solutions of (NH4)2S2O8

2012 ◽  
Vol 5 (1) ◽  
pp. 12-14
Author(s):  
Jan Balej
Keyword(s):  
Activity Coefficient ◽  
Activity Coefficients ◽  
Pure Water ◽  
Relative Activity ◽  
Mean Activity Coefficient ◽  
The Mean ◽  
Water Values ◽  
Mean Activity Coefficients ◽  
Ammonium Peroxodisulfate ◽  
Saturated Solutions

Solubility in the System (NH4)2S2O8—NH3—H2O and Mean Activity Coefficients of Saturated Solutions of (NH4)2S2O8The solubility data of ammonium peroxodisulfate in aqueous ammonia solutions at 15.5 °C have been evaluated using the relative activity coefficient expansion. Using the known value of the mean activity coefficient of saturated solution of ammonium peroxodisulfate in pure water, values of the mean activity coefficients of this salt in the saturated solutions of the given system have been calculated.

Retention Models on Core–Shell Columns

2017 ◽  
Vol 100 (6) ◽  
pp. 1636-1646 ◽  
Author(s):  
Pavel Jandera ◽  
Tomáš Hájek ◽  
Marie Růžičková
Keyword(s):  
Organic Solvent ◽  
Stationary Phase ◽  
Mobile Phase ◽  
High Pressures ◽  
Volume Fraction ◽  
Pure Water ◽  
Core Shell ◽  
Solid Core ◽  
Retention Factors ◽  
Two Parameter

Abstract A thin, active shell layer on core–shell columns provides high efficiency in HPLC at moderately high pressures. We revisited three models of mobile phase effects on retention for core–shell columns in mixed aqueous–organic mobile phases: linear solvent strength and Snyder–Soczewiński two-parameter models and a three-parameter model. For some compounds, two-parameter models show minor deviations from linearity due to neglect of possible minor retention in pure weak solvent, which is compensated for in the three-parameter model, which does not explicitly assume either the adsorption or the partition retention mechanism in normal- or reversed-phase systems. The model retention equation can be formulated as a function of solute retention factors of nonionic compounds in pure organic solvent and in pure water (or aqueous buffer) and of the volume fraction of an either aqueous or organic solvent component in a two-component mobile phase. With core–shell columns, the impervious solid core does not participate in the retention process. Hence, the thermodynamic retention factors, defined as the ratio of the mass of the analyte mass contained in the stationary phase to its mass in the mobile phase in the column, should not include the particle core volume. The values of the thermodynamic factors are lower than the retention factors determined using a convention including the inert core in the stationary phase. However, both conventions produce correct results if consistently used to predict the effects of changing mobile phase composition on retention. We compared three types of core–shell columns with C18-, phenyl-hexyl-, and biphenyl-bonded phases. The core–shell columns with phenyl-hexyl- and biphenyl-bonded ligands provided lower errors in two-parameter model predictions for alkylbenzenes, phenolic acids, and flavonoid compounds in comparison with C18-bonded ligands.

Decoration of specific sites on freeze-fractured membranes

1978 ◽  
Vol 36 (2) ◽  
pp. 140-141
Author(s):  
H. Gross ◽  
H. Moor
Keyword(s):  
Pure Water ◽  
Freeze Fracture ◽  
Chemical Properties ◽  
Surface Forces ◽  
Sulfate Pentahydrate ◽  
Copper Sulfate Pentahydrate ◽  
Physico Chemical ◽  
Water Of Hydration ◽  
Small Container ◽  
Binding Forces

Fracturing under ultrahigh vacuum (UHV, p ≤ 10-9 Torr) produces membrane fracture faces devoid of contamination. Such clean surfaces are a prerequisite foe studies of interactions between condensing molecules is possible and surface forces are unequally distributed, the condensate will accumulate at places with high binding forces; crystallites will arise which may be useful a probes for surface sites with specific physico-chemical properties. Specific “decoration” with crystallites can be achieved nby exposing membrane fracture faces to water vopour. A device was developed which enables the production of pure water vapour and the controlled variation of its partial pressure in an UHV freeze-fracture apparatus (Fig.1a). Under vaccum (≤ 10-3 Torr), small container filled with copper-sulfate-pentahydrate is heated with a heating coil, with the temperature controlled by means of a thermocouple. The water of hydration thereby released enters a storage vessel.

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