Kunishige Naito

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 partition chromatography : Quantitative evaluation

Abstract The retention mechanism in gas-liquid chromatography has been studied for hydrocarbon-silicone DC 200 and -Oronite polybutene 128 systems. Plots of VE/WL against Wz/WL for each solute could be approximated by four straight lines with different slopes and intercepts and three straight lines when silicone DC 200 and Oronite polybutene 128 were loaded on modified alumina, respectively. Satisfactory results were obtained on analysis of the retention data with the equations that describe these straight lines, derived on the basis of the possible distribution of the liquid phase on the solid support with heterogeneous surface dispersing more and less adsorptive sites.

Adsorption effects in gas-liquid partition chromatography☆

Abstract Contributions of adsorption on the surface of the support and/or stationary phase in gas-liquid partition chromatography were investigated by using an adsorption-active support and squalene, di-n-octyl phthalate, di-n-octyl sebacate or 1,2,3-tris(2-cyanoethoxy)propane as stationary phase. Adsorption effects vary with the adsorptivity of the support, the polarity of the stationary phase and the amount of the phase loaded on the support. Retention volumes of saturated and unsaturated hydrocarbons in the low liquid-loading range can be expressed in terms of the gas-liquid partition and adsorption on clean and liquid-coated support surfaces. The interaction of the solute with the surface of support is also discussed.

The separation of aluminum(III) ions from the aqueous solution on membrane filter using Alizarin Yellow R

The membrane filtration was examined as an effective and selective method for collection of Al(III) ions from aqueous solutions using Alizarin Yellow R, one of a pH-indicator, as a precipitating reagent. For preparation of aqueous solutions without precipitate or turbidity, a non-ionic surfactant, Triton X-100, was used as a solubilizing reagent for insoluble materials. Three metal ions, Al(III), V(III) and Cu(II) ions, were able to be collected as yellow-orange precipitates from aqueous solutions controlled in a range of pH 4-7, pH 4-9, and pH 5.5-12, respectively, on a membrane filter by filtration under suction. Hydrogen peroxide and o-phenanthroline were found to be capable of masking V(III) and Cu(II) ions in a range of pH 5.5-8 in which Al(III) ions were collected. This membrane filtration was applied to selective separation and determination of Al(III) ions in tap water.

Adsorption effect on the retention volume of hydrocarbons and dialkyl ethers in gas—liquid chromatography using a polar stationary phase and silica gel support

Abstract The mechanism of solute retention in gas—liquid chromatography was studied by using silica gel coated with different amounts of polyethylene glycol 20 000 (PEG 20M). The retention volumes of aliphatic hydrocarbons, aromatic hydrocarbons and dialkyl ethers were determined as a function of liquid phase loading. The silica gel surface showed homogeneous characteristics on adsorption of saturated hydrocarbons and a heterogeneous nature on adsorption of the other solutes. The experimental data could be interpreted on the basis of a model in which the silica gel surface was covered first with a monolayer and then with a double layer of PEG 20M. Distribution constants of adsorption on the silica gel, on the monolayer and on the double layer were calculated.

The reactions of polythionates: Kinetic of the cleavage of trithionate ion in aqueous solutions

Abstract A kinetic study of the cleavage of trithionate has been made in water over the temperature range of 40–80°C, and in aqueous ammonia solutions over the range of 40–70°C. In aqueous ammonia, the ammonolytic reaction of trithionate was found to proceed in competition with the hydrolytic one. For both reactions, a rate law of the form, -d[S 3 O 6 2 ]/d t = k a [NH 3 ][S 3 O 6 2− ] and -d[S 3 O 6 2− ]/d t = k w [H 2 O][S 3 O 6 2− ], was obtained. In the presence of thiosulfate, the thiosulfate-trithionate reaction, described by, -d[S 3 O 6 2− ]/d t = k t [S 2 O 6 2− ][S 3 O 6 2− ], may proceed in parallel with either or both the above solvolytic reactions. The activation parameters suggest that the mechanism of the solvolytic reactions differs from that of the thiosulfate-trithionate reaction which is expected to involve a nucleophilic displacement at the bivalent sulfur in trithionate. A mechanism of the cleavage of trithionate supported by the kinetic results has been proposed.

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.

Mixed retention mechanism in gas—liquid chromatography of hydrocarbon and dialkyl ether solutes on squalane-coated silica gel

Abstract A mixed retention mechanism in gas—liquid chromatography was studied in order to elucidate the dependence of the retention volume of some hydrocarbons and dialkyl ethers on squalane-coated silica gel on the liquid phase loading. Two adsorption equilibria on the solid surface of silica gel and the surface of a monolayer of squalane dominantly contribute to solute retention until the monolayer of squalane is formed on the silica gel surface. Subsequently, excess of squalane formed a double layer on the deactivated surface of the silica gel, so bulk solution partition concurrently contributes to solute retention together with adsorption equilibria on the monolayer and/or the double layer of squalane. The distribution constants of bulk solution partition and adsorption equilibria on the solid surface of silica gel and the surface of the monolayer of squalane were calculated as reasonable values for any solute.

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.