Accurate Measurements of Infinite Dilution Activity Coefficients Using Gas Chromatography with Static-Wall-Coated Open-Tubular Columns

Abstract

Wall-coated open-tubular (WCOT) columns provide higher column efficiency and lower solute interfacial adsorption effect than packed columns. However, previous efforts used to measure the infinite dilution activity coefficient (γ(∞)) via a chromatographic technique have used packed columns, because the low carrier gas flow rate (U) and the small stationary phase amount (n(2)) in WCOT columns raise large errors. By rationally revising the γ(∞)-calculation equation for static-wall-coated open-tubular column, we observed that U and n(2) are not necessarily needed and the resulting error could be reduced, and WCOT column gas chromatography subsequently became a superior method for the accurate γ(∞) determination. In this study, we validate our revised γ(∞)-calculation equation by measuring γ(∞) in an ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate system, in which 55 organic compounds covering a wide range of functional groups were used as probe solutes and their γ(∞) values in the ionic liquid were determined at 40.0, 50.0, and 60.0 °C. Experimental error analysis shows that our revised equation remarkably reduces the error compared to the common γ(∞)-calculation equation. Our data is consistent with previously reported values obtained via other techniques, which further proves the credibility of our revised equation. The accurately determined γ(∞) values can be directly used to calculate the partial molar excess enthalpy, selectivity, and capacity, which will benefit for the rapid screening of solvents (especially ionic liquids) in separation approaches.

Uncovering the Critical Factors that Enable Extractive Desulfurization of Fuels in Ionic Liquids and Deep Eutectic Solvents from Simulations

“…The μ i ex,∞ values were calculated here for the ILs/TS systems using FEP–MD simulations in conjunction with the 0.8*OPLS-2009IL and OPLS–VSIL FFs (Table and Figure ). Reported experimental measurements − and theoretical estimations of γ i ∞ (Table S5) were converted to μ i ex,∞ using eq and provided for comparison (Table and Figure ). In the [BMIM]­[Cl]/TS system, the μ i ex,∞ computed using OPLS–VSIL FF was −4.298 ± 0.045 kcal/mol, which was reasonably close to the experimental value −4.151 kcal/mol, whereas the 0.8*OPLS-2009IL FF gave a larger deviation with a value of −4.571 ± 0.061 kcal/mol.…”

“… a Calculated from γ i ∞ generated using the least-squares vector machine (LSSVM) method by Paduszyński b Calculated using experimentally reported γ i ∞ values. − …”

Overview of Activity Coefficient of Thiophene at Infinite Dilution in Ionic Liquids and their Modeling Using COSMO-RS

“…Effect of anion for [C 4 C 1 im] + cation based ILs. Symbols: (dark blue *, --) [C 4 C 1 im]­[OctSO 4 ], (bronze ×, --) [C 4 C 1 im]­[BETI], (▲, --) [C 4 C 1 im]­[TOS], (light blue ●, --) [C 4 C 1 im]­[CF 3 SO 3 ], (green ⧫, --) [C 4 C 1 im]­[SCN], (orange +, --) [C 4 C 1 im]­[PF 6 ], and (red ■, --) [C 4 C 1 im]­[BF 4 ] …”

Desarrollo de columnas capilares con líquidos iónicos como fases estacionarias para cromatografía de gases

“…Tabla 4-10 Selectividad a dilución infinita para varios pares críticos de relevancia en distintos líquidos iónicos con el catión tri(hexil)tetradecilfosfonio. Las selectividades obtenidas con líquidos iónicos de fosfonio suelen ser inferiores a las informadas en bibliografía para líquidos iónicos de imidazolio [51], [52], [62] y su utilidad para esas separaciones es limitada. Una excepción notable es la selectividad calculada para el par hexano/ cloroformo en el líquido iónico THTDP-Br.…”

“…Debe recordarse que tiempos de retención independientes del tamaño de la muestra no significa necesariamente la ausencia de fenómenos de adsorción; pueden obtenerse picos simétricos con tiempo de retención invariante si todos los mecanismos de retención ocurren en condiciones de dilución infinita.Es evidente que el error introducido al aproximar el tiempo muerto con el tiempo de elución de metano es muy bajo para una columna capilar. En este trabajo de tesis, empleando columnas capilares y fases estacionarias altamente polares en las que se espera que el coeficiente de partición del metano sea muy bajo, podemos asumir que esta aproximación no introduce un error significativo y dada su simplicidad, su utilización es razonable.Conclusiones similares se han reportado en el trabajo de Xu[51] con un líquido iónico de imidazolio depositado en columnas capilares para la obtención de coeficientes de actividad.Experimentalmente, la medición del tiempo muerto de esta manera implica la coinyección de vapores del soluto junto con un volumen de metano. La inyección simultánea también permite corregir pequeñas fluctuaciones en el caudal del gas portador.…”