Adsorption in gas-liquid chromatography

Behavior of n-alkanes on poly(oxyethylene) capillary columns. Evaluation of interfacial effects

The solvation behavior of n-alkanes on poly(oxyethylene) was studied employing capillary gas chromatography. Interfacial effects were discriminated and evaluated through the analysis of retention data from six commercial fused-silica capillary columns, having film thicknesses of 0.15-5 microm. Expressions for the mixed retention mechanism in capillary columns were deduced from assumptions of a general character. Partition coefficients were determined for the n-alkanes up to 28 carbon atoms, at temperatures ranging from 40 to 240 degrees C. In agreement with other authors, it was observed that interfacial phenomena contribute poorly to the chromatographic retention, being negligible over 140 degrees C for homologues with less than 16 carbons.

Gas chromatographic measurement of volatility of herbicide esters

The vapour pressures of eleven herbicide esters were calculated from gas chromatographic measurement of relative retention volumes (dibutyl phthalate = 1) on a non-polar SE-30 column. Measurements were made at temperatures from 72 to 182 degrees C, but by assuming that the ratio of the latent heat of vaporization of the ester to that of dibutyl phthalate was independent of temperature, values for vapour pressure could be extrapolated to 25 degrees C. Vapour pressures at 25 degrees C ranged from 2.5.10(-4) mmHg for 2,4-D ethyl ester to 1.9.10(-7) mm Hg for picloram isoocytly ester.