Sadaaki Moriguchi

Characterization of modified alumina as an adsorbent for gas-solid chromatography : Salt loading dependence of retention volume on modified alumina adsorbent coated with potassium carbonate

Abstract The retention mechanism in gas—solid chromatography has been studied for alumina adsorbents modified by pre—heating and subsequent coating with various amounts of potassium carbonate. Four salt loading regions could be characterized. The salt loading dependence of the specific surface area of the modified adsorbent could be approximated as a linear relation. A model for the salt-modified adsorbent surface is described in which the base alumina adsorbent surface is gradually covered with two types of salt layers, first a monolayer and secondly a crystalline layer. The solute retention in gas—solid chromatography could be interpreted on the basis of a linear combination of concurrent contributions from adsorption equilibria on subsurfaces distributed on the adsorbent. Acceptable results were obtained through analysis of experimental data.

Adsorption effects in gas-liquid chromatography: solute retention in the hydrocarbon solute-polar liquid stationary phase (triton x-100) system

Abstract A model for the distribution of liquids on modified alumina is described, in which the solid support is successively covered first with a monolayer, then with a double layer and finally with a bulk liquid layer of Triton X-100. On the basis of this model, the solute retention can be interpreted as a linear combination of concurrent contributions of possible sorption equilibria on the subsurfaces and/or in the bulk liquid layer. Acceptable results were obtained by analysis of experimental data.

Adsorption effects in gas-liquid chromatography : Solute retention in the hydrocarbon solute-polar stationary phase (polypropylene glycol 2000) system

Abstract The solute retention mechanism in gasliquid chromatography was studied in a non-polar hydrocarbon solutemoderately polar stationary phase (polypropylene glycol 2000) system. The dependences of the retention volume of a solute and the specific surface area of column packings on the liquid loading are quantitatively interpreted on the basis of a model for the distribution of a liquid phase on a solid support. In the model, the solid support surface is assumed to be successively covered with three different types of liquid phase layers, first with a monolayer, second with a double layer and finally with a bulk liquid layer, as the liquid loading increases. The changes in the enthalpy and entropy of solution and adsorption were calculated from distribution constants for bulk solution partition and for interfacial adsorption obtained by analysis at two column temperatures.

Contributions to hydrocarbons retention in gas—liquid—solid chromatography with polyethylene glycol 6000 as stationary phase

Abstract The contribution of interfacial adsorption and bulk solution partition to hydrocarbon solute retention on polyethylene glycol 6000 (PEG 6000) were investigated by gas—liquid—solid chromatography using Chromosorb P and modified alumina supports pre-heated at 900, 1000, 1100 and 1150°C. When using a solid support with low adsorption capacity such as Chromosorb P, the bulk solution partition controlled the retention volume of a given solute. On a solid support with high adsorption capacity, the interfacial adsorption was still important even at a high liquid loading. These results can be interpreted in terms of the thickness of the PEG 6000 layer on the solid support. On the modified alumina, at least a triple layer was required for the PEG 6000 to exhibit its bulk proporties.

Characterization of modified alumina as an adsorbent for gas—solid chromatography : Modification with ammonium flouride

Abstract Modification of the adsorptivity of alumina by coating it with ammonium flouride, with thermal treatment before and after coating, has been investigated. When the coated alunmina is thermally treated, the retention volumes of solutes increase on increasing the heating temperature from 200 to 600°C and then decrease with a further increase by above 600°C. It is considered that this increase in retention volume is due to decomposition of the ammonium hexafluoroaluminate formed by reaction of the alumina with ammonium fluoride ad concurrent formation of β-aluminum flouride on the alumina surface. Optimal conditions for the preparation of the modified alumina with good characteristics for gas—solid chromatography involve selecting a post-heating temperature at which any conversion of ammonium hexafluoroaluminate into other compounds, especially β-aluminum fluroide, is prevented.

Adsorption effects on retention behaviour of hydrocarbons in gas-liquid and gas-solid chromatography with the use of modified alumina coated with diphenyl phthalate as column packings

Abstract Adsorption effects on the retention of hydrocarbons were investigated in gas-liquid-solid chromatography using modified alumina beads, preheated at 1150 and 1200°C, coated with diphenyl phthalate as column packings. At a column temperature above the melting point of diphenyl phthalate. the same method as used in a previous study could be applied for interpreting the solute retention behaviour. At a column temperature below the melting point of the stationary phase, the retention mechanism could be successfully understood by considering that some adsorption equilibria took part in solute retention on the basis of the distribution of diphenyl phthalate in a solid form on the modified alumina surface.

Characterization of modified alumina as an adsorbent for gas-solid chromatography : Modification with dipotassium hydrogen phosphate

Abstract The change in surface properties of modified alumina adsorbents for gas-solid chromatography (GSC) has been studied by coating alumina with dipotassium hydrogen phosphate and heating before and/or after coating. The surface properties were significantly influenced by some thermally induced changes, such as sintering, dehydration and crystallization due to a phase transition of alumina, mainly as a result of the pre-heating treatment and also of the pyrolysis of the salt and recrystallization of its product after fusion in the post-heating treatment. A dependence of solute retention volume on the temperature of heat treatment could be interpreted in terms of changes of the surface properties caused by successive coverage of the alumina surface with a monolayer, a double layer and finally a crystalline layer of the salt. The same reasoning could be applied the dependence of solute retention volume upon salt loading. The total weight of free alumina packed into the column was found to be an important parameter for describing the characteristics of the GSC column.

Characterization of modified alumina as adsorbent for gas-solid chromatography. Modification of alumina with potassium fluoride-hydrofluoric acid mixed solution

SummaryThe adsorption characteristics of alumina to hydrocarbons are varied by its impregnation with a mixed solution of potassium fluoride-hydrofluoric acid followed by thermal treatment. The adsorptive property of the alumina is decreased with the increase of concentration of potassium fluoride in the mixed solution and of the heating temperature. The surface layer of the modified alumina seems to consist of potassium fluoroaluminate, KxAlF3+x; with the increase of x the adsorptive property to hydrocarbons is decreased. The adsorptive property of alumina to hydrocarbons can be controlled by selecting the composition of the mixed solution and the temperature of heating after the treatment with the mixed solution.Modified alumina prepared by the present method has adsorption characteristics of Type II according to Kiselevs classification.