Gas-liquid partition chromatography; the separation and micro-estimation of volatile fatty acids from formic acid to dodecanoic acid.

Industry has long used charcoal or other solid absorbents in columns for cleaning gas streams or for solvent recovery, and more recently Turner (1943), Claesson (1946), Glueckauf, Barker & Kitt (1949), Phillips (1949) and Turkel'taub (1950) have used charcoal in gas chromatograms for the analysis of hydrocarbons and esters. Gas-liquid scrubbing columns have been used in industry for many years but, though Martin & Synge (1941) suggested the use of gas-liquid partition chromatograms for analytical purposes, no work has been reported along these lines. This paper presents modifications necessary to the theory of Martin & Synge (1941) to allow for the compressibility of the mobile phase and describes the application ofthe gas-liquid partition chromatogram to the separation of volatile fatty acids. The separations obtainable by this method are essentially parallel to those obtainable by distillation, but good separations can be achieved much more easily and it is possible to work with very much smaller quantities. In fact, the lower limit of quantity of material used is determined only by the efficiency of detection. In general, far less trouble from azeotrope formation is to be expected, since the concentrations of the substances to be separated in the liquid phase are always low and it may be possible to choose a liquid phase which associates only with one component of the azeotrope. Work on a preparative scale, though theoretically possible, is likely to be inconvenient because of the bulk of the apparatus. The method of detection described here is acid-base titration, but many methods of detecting changes in the composition ofa gas stream could be used and it is intended in future publications to explore some of these, which should extend the range of application to all substances capable of being distilled at the pressure of a few mm. of mercury. In suitable cases the gas-liquid partition column has two principal advantages over the ordinary liquid-liquid partition column: (a) the low viscosity of the mobile phase allows relatively longer columns to be used with a corresponding gain in efficiency and (b) in general it is easier to detect changes in composition of a gas than of a liquid stream. A THEORY OF GAS-LIQUID PARTITION CHROMATOGRAPHY