Shinsuke Takei

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.

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.

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.

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.

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.

Solvent extraction of tripropyltin(IV) carboxylate complexes

Abstract The distribution of Pr 3 Sn(IV) between aqueous acetic, monochloroacetic, dichloroacetic or formic acid and carbon tetrachloride at ionic strength of 0·1 or 0·5 has been studied. The distribution ratio of Pr 3 Sn(IV) could be explained by the relation, D = [ Pr 3 Sn(IV) ] org,total [ Pr 3 Sn(IV) ] aq,total = [ Pr 3 Sn A] org ([ Pr 3 Sn + ] + [ Pr 3 Sn A] , where A denotes CH 3 COO-, CH 2 ClCOO-, CHCl 2 COO- or Hence, the stability constants, K , and the partition constants, P , of carboxylate complexes have been obtained as follows: P K Pr 3 SnOOCCH 3 6·9 4·3 × 10 3 Pr 3 SnOOCH 7·9 4·5 × 10 2 Pr 3 SnOOCCH 2 Cl 6·8 × 10 1 5·3 × 10 1 Pr 3 SnOOCCHCl 2 2·5 × 10 3 2·5 μ = 0·1 18°C Comparison of stability constants and acid dissociation constants reveals a linear relation between them.