Role of the liquid phase in gas-liquid-solid chromatography and its influence of column performance. Experimental approach

Discussion of thermodynamic data obtained by adsorption gas chromatography of hydrocarbons on a new graphitized carbon black with a high specific surface area

“…After these sites have been filled by increasing the percentage of squalane, the heat of adsorption might be expected to be constant and to correspond to that given by adsorption on the homogeneous surface. Contrary to this expectation, the isosteric heat of adsorption increases again to a maximum as a consequence of lateral interactions, followed by a decrease in the monolayer region [21 ]. The curve is very similar to that obtained for hydrogen-treated Carbopack C [31 ].…”

“…This can be explained by the probable presence of cavities of molecular dimensions, where adsorption takes place rather than on the flat surface and where the number of degrees of freedom of the molecule decreases, as does entropy [21 ]. In fact, passing from adsorption on the flat carbon surface to adsorption in cavities with molecular dimensions should result in a loss of two degrees of translational freedom parallel to the surface, replaced by two external vibrations acquired by the adsorbed molecules.…”

“…There is a constant increment of about 8 kJmo1-1 per CH2 in AG ~ (Troube's effect-the adsorbates are adsorbed in a ,lying down' position and not in a ,standing-on-end' position [21]). The adsorption process is more spontaneous on Carbograph 5, as expected; in fact, AG ~ values are higher than for Carbopack C and Carbopack B, as shown in Table V.…”

“…Graphitized carbon blacks (GCBs) have been extensively studied and several types are widely used as standard adsorbents in solid-phase extraction, in air sampling [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], and as stationary phases in gas-liquidsolid chromatography [21][22][23][24][25][26][27][28][29]. GCBs are obtained by heating carbon black at high temperature (3000 ~ in an oxygen-free atmosphere [3,22].…”

A bonded polyoxyethylene phase for gas and liquid chromatography

“…In a-wider context, layers oriented within the range of surface forces are fascinating though complex objects of study. The interests involved range from basic investigations in physical chemistry (55,56) and chromatography (57)(58)(59)(60)(61)(62)(63)(64)(65), over biological interfaces, adhesive joints, and the oceans' top layer, to dishwashing (66,67). Some physicochemical aspects of thin layers, as seen by gas chromatography, have been reviewed (68).…”