Gas-Liquid Chromatography

Fig.1 shows a scheme of the home-made GLC-apparatus which can be used for "classical" as well as for "non-steady-state" gas-liquid chromatography <1, 2>. The calculation of g¥ from the obtained data and some typical g¥-values can be seen in Fig. 2 and 3.

Fig. 1: Scheme of the gas-liquid chromatograph

Fig. 1:   Scheme of the gas-liquid chromatograph applicable
         in the "classical" and the "non-steady-state" mode

 

 

Fig2.: Evaluation of chromatographic data

Fig. 2:   Evaluation of chromatographic data


More Information about the data evaluation

 

Fig. 3: Typical gamma results

Fig. 3:   Typical g¥-results

The GLC  technique requires the careful preparation of the column and allows the measurement of a great number of g¥  in a rather short time. The amount of solvent in the column has been determined gravimetrically. In order to check if solvent losses occur during the measurements, the liquid loading is determined before and after the measurement. This is taken into account assuming linear solvent loss during the isothermal measurements. With the use of presaturators the loss of solvent can be kept to a minimum. Furthermore the experimental conditions (gas flow, solvent loss, ...) were checked by measuring the retention time of a reference substance in regular intervals.

 

Dilutor Method

The experimental setup for the dilutor method is shown schematically in Fig. 4. and Fig. 5

Exp_Dil_Fig1.gif (34278 Byte)

Fig. 4:   Scheme of the dilutor

 

picture of the device   Dilutor


Fig. 5:   Scheme of the equilibrium cell

Fig. 5:   Scheme of the equilibrium cell

With a constant inert gas flow a highly diluted component (solute) is stripped from a liquid solution (solvent). The variation of solute concentration in the gaseous phase is measured with the help of a gas chromatograph <3>. In Fig. 6 values for g¥ are obtained from the graph t vs. ln peak area (concentration of the solute in the vapor phase).

Fig. 6   Evaluation of data from the dilutor method

                                Fig. 6    Evaluation of data from the dilutor method                               

A detailed description of the measurement procedure and the data analysis can be found by Leroi et al. (1977) and Duhem and Vidal (1978). The real behavior of the gas phase is taken into account with the help of fugacity coefficient of the solute in the saturated state. The values are calculated with the help of the second virial coefficient. For the vapor pressure calculation (Antoine, Wagner, DIPPR, ...)  the equation with  the smallest deviations to  experimental vapor pressure data stored in the Dortmund Data Bank is used.

 

References

  1. Schiller, M.; Gmehling, J. Measurement of Activity Coefficients at Infinite Dilution Using Gas-Liquid Chromatography. 4. Results for Alkylene Glycol Dialkyl Ethers as Stationary Phases. J. Chem. Eng. Data, 1992, 37, 503-508.
  2. Dallinga, L.; Schiller, M.; Gmehling, J. Measurement of Activity Coefficients at Infinite Dilution Using Differential Ebulliometry and Non-Steady-State Gas-Liquid Chromatography. J. Chem. Eng. Data 1993, 38, 147-155.
  3. Leroi, J.-C.; Masson, J.-C.; Renon, H.; Fabries, J.-C.; Sannier, H. Accurate Measurement of Activity Coefficients at Infinite Dilution by Inert Gas Stripping and Gas Chromatography. Ind. Eng. Chem., Process Des. Dev. 1977 ,16(1), 139-144
  4. Duhem, P.; Vidal, J. Extension of the Dilutor Method to Measurement of High Activity Coefficients at Infinite Dilution. Fluid Phase Equil., 1978, 2, 231-235.
  5. Gmehling, J.; Kolbe, B. Thermodynamik, 2nd ed.; VCH-Verlag: Weinheim, 1992.
  6. Gmehling, J.; Menke, J.; Schiller, M. Activity Coefficients at Infinite Dilution, DECHEMA Chemistry Data Series IX, DECHEMA: Frankfurt, 1994; Parts 1-4.
  7. Gruber, D.; Langenheim, D.; Moollan, W.C.; Gmehling, J. Measurement of Activity Coefficients at Infinite Dilution Using Gas-Liquid Chromatography. 6. Results for Systems Exhibiting Gas-Liquid Interface Adsorption with 1-Octanol as Solvent. J. Chem. Eng. Data, 1997, 42, 882-885.
  8. Gruber, D.; Langenheim, D.; Moollan, W.C.; Gmehling, J. Measurement of Activity Coefficients at Infinite Dilution Using Gas-Liquid Chromatography. 7. Results for Various Solutes with N-Methyl-2-piperidone as Stationary Phase. J. Chem. Eng. Data, 1998a, 43, 226-229.
  9. Gruber, D.; Topphoff, M.; Gmehling, J. Measurement of Activity Coefficients at Infinite Dilution Using Gas-Liquid Chromatography. 8. Results for 22 Solutes in Tetraethylene Glycol Dimethyl Ether and 18 Solutes in Triethylene Glycol Dibutyl Ether. Int. Electron. J. Phys.-Chem. Data, 1998b, 3, 215-224.
  10. D. Gruber, M. Topphoff, J. Gmehling; Measurement of Activity Coefficients at Infinite Dilution Using Gas-Liquid Chromatography, 9. Results for Various Solutes with the Stationary Phases 2-Pyrrolidone and N-Methylformamide; J. Chem. Eng. Data 43, 935-940 (1998)
  11. D. Gruber, M. Krummen, J. Gmehling; Bestimmung von Aktivitätskoeffizienten bei unendlicher Verdünnung mit Hilfe der Dilutor-Technik; Chem.- Ing.- Tech. 71, 503-508 (1999).

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