Gas-liquid chromatographic determination of cross-term second virial coefficients using glycerol. Benzene + nitrogen and benzene + carbon dioxide at 50°C

Abstract

This paper extends the theory of gas-chromatographic elution of a highly dilute solute to the second order in gas-phase imperfection terms, yielding a precise expression for the ideal retention volume in terms of the thermodynamic parameters of the system. The effect of carrier gas dissolution in the solvent is included explicitly ; the cross-term second virial coefficient Bl for the system solute+ carrier gas cannot be evaluated unambiguously for an appreciably soluble carrier gas. The use in such cases of polar solvents in which non-polar carrier gases are effectively insoluble is discussed with reference to surface adsorption and chromatographic non-ideality, which are important in polar solvents. Extrapolation of observed retention volume to zero flowrate for each of a series of columns covering a range of solvent loadings should give, corresponding to the limit of infinite loading, unambiguous values of bulk-phase solutein-solvent activity coefficient and of B1 2. The theory has been applied to measurements on the systems benzene+nitrogen+glycerol, and benzene+ carbon dioxide+glycerol, using four columns loaded at 15-7,25.3,33*6 and 23-3 % by weight glycerol on Celite, and the system benzene+hydrogen+glycerol using a column loaded at 44.0 %. The flowrate-dependence of the net retention volume is approximately linear on all columns, the gradient correlating well with empirical plate height and with solvent loading, in accordance with theory and with the known facts about the distribution of a polar solvent on Celite. The zero-flowrate Biz values are effectively the same with all columns. These values of Blz at 50°C are, for benzene+ nitrogen, -98f9 cm3 mole-l, and for benzene+carbon dioxide, -2503~15 cm3 mole-l, both being in fair agreement with theoretical predictions for systems of non-spherical molecules of different sizes. The activity coefficient for benzene at infinite dilution in glycerol at 50°C is logy: = 2.0841 0 0 0 5 .

The determination of activity coefficients of hydrocarbons at infinite dilution using a g.l.c. technique with the polar solvent tetrahydrothiophene-1,1-dioxide,c-(CH2)4SO2, (sulfolane) at the temperature 303.15 K

“…Everett and Cruickshank et al (6,7) developed equation (1) for obtaining the activity coefficient g a 13 at infinite dilution of a volatile solute in an involatile solvent from g.l.c. results:…”

The determination of activity coefficients of alkenes, alkynes, and cycloalkanes at infinite dilution with the polar solvent tetrahydrothiophene-1,1-dioxide (sulpholane) using a g.l.c. technique atT=303.15 K andT=313.15 K

“…The activity coefficients at infinite dilution g a 13 were determined using the equation developed by Everett (5) and Cruickshank et al, (6) and described by Letcher:…”

Determinação do coeficiente de atividade em diluição infinita de hidrocarbonetos em furfural a 298,15 K por SPME-GC/FID

“…3,4 Onde n 2 L é o número de moles de solvente na fase líquida, P 1 sat é a pressão de saturação do soluto, R a constante dos gases, T a temperatura, B 11 o segundo coeficiente de Virial do soluto e v 1° o volume molar do soluto.…”

“…Muitas técnicas vêm sendo desenvolvidas ao longo dos anos para a determinação dos coeficientes de atividade em diluição infinita para misturas líquidas, sendo algumas mais complexas e custosas, como o GLC (Gas-Liquid Chromatography), [3][4][5] e absorção gasosa com gás inerte não solúvel (Gas-Stripping). 5,6 Na técnica de GLC uma coluna cromatográfica com um suporte inerte é empacotada com um solvente líquido não volátil como fase estacionária.…”