Solid phase microextraction using fused silica fibers coated with graphitized carbon black

Summary This paper presents the results obtained using fused-silica fibers coated with graphitized carbon black (Carbograph-Alltech) for solid-phase microextraction (SPME). The extraction and calibration curves relative to organic micro-pollutants present in gaseous and aqueous samples are reported. Examples of applications of this extraction procedure to GC and GC-MS analysis of organic micro-pollutants in actual samples are also reported.     

Adsorption behavior of Vulkan-7H graphitized carbon black

The adsorption behavior of Vulkan-7H carbon black graphitized at 3073 K was studied. Benzene adsorption isotherms at 293 K were measured by the static method and by gas chromatography. It was shown that Vulkan-7H carbon black may be considered as a supermicroporous adsorbent with a pore size of 1.05 nm.The sample was provided by N. N. Lezhnev.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1544–1546, September, 1993.     

Adsorption of cyclic amines on graphitized thermal carbon black

Thermodynamic characteristics of adsorption (TCA) for aniline and its methyl derivatives on the surface of graphitized thermal carbon black (GTC, Carbopack C HT trade mark) were determined using equilibrium gas adsorption chromatography in the range of the lowest adsorbate concentrations in the gas phase. A series of relationships relating the TCA of the studied amines to their physicochemical parameters was obtained. The theoretical values of entropy of adsorption were calculated in the framework of the model of two-dimensional ideal gas and compared with the corresponding experimental values, which allowed one to reveal specific features of the molecular structure of the adsorbates. A similarity between the thermal component of entropy of the studied compounds in the adsorbed state and that of the entropy of the pure liquid adsorbates made it possible to refine the physical state and mobility of the adsorbate molecules in the force field of the adsorbent. The regression equation relating the heats of adsorption on the GTC to such molecular constants of adsorbates as polarizability, molecular surface area, and molecular weight were proposed for the first time. A high predictive power of the equations derived in the work for the preliminary estimation of the adsorption characteristics of alkylanilines and alkylbenzenes on the GTC was shown.     

Adsorption of adamantanol isomers on graphitized thermal carbon black

The thermodynamic characteristics of adsorption of some adamantanol isomers on graphitized thermal carbon black were calculated and determined experimentally. The parameters of the potential function for the intermolecular interaction between hydroxyl oxygen and carbon of the graphite basis plane were determined for the first time. The adsorption properties of adamantanols are largely determined by electron density distribution in the adamantane cage, which are related to the cage effect.     

Adsorption equilibria of binary gas mixtures on graphitized carbon black

Adsorption equilibria for binary gas mixtures (methane-carbon dioxide, methane-ethane, and carbon dioxide-ethane) on the graphitized carbon black STH-2 were measured by the open flow method at 293.2 K. The experimental pressure range was (0 to 1.6) MPa. The extended Langmuir (EL) model and the ideal adsorption solution theory (IAST) have been adopted to predict the equilibria of binary gas mixtures. The results indicate that gas mixtures adsorbed on the homogeneous surface of STH-2 exhibit the nonideal behavior, which is mainly induced by adsorbate-adsorbate interactions. The real adsorption solution theory (RAST) has been used to analyze the property of the adsorbed mixtures. The activity coefficients have been correlated with the Wilson equation. The investigation demonstrates that the nonideality of adsorbed phase is completely dissimilar with the bulk liquid phase. The adsorption of the heavier component would benefit the adsorption of the lighter component.     

The nature of surface chemical heterogeneities of graphitized carbon black

Experimental evidence is presented for the existence of quinone, aromatic ether, carboxylic acid and phenol groups on the surface of a graphitized carbon black (GCB), that is P-33 (2700°C). This evidence has been achieved by using polarographic analysis of a slurry of GCB particles.Polarographic analysis has been also performed for ungraphitized P-33.By comparison, it appears that the heating at 2700°C does not remarkably change the nature and the amount of chemical groups chemically bound to the surface of the carbon black.     

Gas chromatographic investigation of adsorption equilibria on graphitized thermal carbon black

Summary Retention volumes and heats of adsorption at low surface coverages of graphitized thermal carbon black (GTCB) for C₆–C₁₄ aromatic hydrocarbons have been determined. The dependence of heats of adsorption of these molecules on their structure and the number of carbon atoms in the molecule have been investigated. Substitution in the ring in methylbenzenes is not equivalent to the lengthening of the side-chain in the isomers of n-alkylbenzenes and gives rise to a much greater increase in the retention volumes and heats of adsorption.     

Retention of some phenyl-substituted and bicyclic hydrocarbons on graphitized carbon black

Summary Retention volume values for zero cample size (Henry's constants) at different temperatures, retention indices and differential adsorption heats of phenylethylene, phenylacetylene, C₉–C₁₂ phenylcyclanes, biphenylethylenes, biphenylacetylene, bicyclohexyl and bicyclohexylmethane have been determined on graphitized thermal carbon black (GTCB). The molecules of all these hydrocarbons are capable of internal rotation. The values of the thermodynamic adsorption characteristics of phenylcyclanes increase with increasing number of carbon atoms in the cycle. Bicyclohexyl is retained on GTCB considerably weaker than biphenyl while bicyclohexylmethane is retained stronger than biphenylmethane. Symmetric and nonsymmetric biphenylethylenes are retained much stronger than the corresponding biphenylethanes. Phenylethylene (styrene) and trans-biphenylethylene (trans-stilbene) are stronger retained on GTCB than phenylacetylene and biphenylacetylene (tolane), respectively. The relationship between the structure of these molecules and their retention on GTCB is discussed.     

The cell effect in adamantane adsorption on graphitized thermal carbon black

Nonequivalence of the nodal and bridging carbon atoms of the adamantane molecule during adsorption on graphitized thermal carbon black was shown. The nonequivalence is related to a special type of intermolecular interaction, the cell effect. Based on the experimental data and the molecular statistical calculations of Henry's constants, the parameters of atomatom potentials for the nodal carbon atoms in the adamantane molecule were found. This atom-atom potential differs from that known for the carbon atom in the sp³-hybridization. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 849–853, May, 2000.     

Solid-phase extraction of aminobenzoic acids and aminotoluenesulfonic acids with graphitized carbon black

The extraction of amphoteric aromatic amines from water samples is difficult because of their high polarity. For the enrichment of aminobenzoic acids and aminotoluenesulfonic acids with solid-phase extraction, graphitized carbon black (GCB) was investigated. With few exceptions, the 12 analytes studied were extracted with recoveries > 60% at neutral or basic pH, whereas at pH 3 low recoveries were obtained. Addition of salt caused a decrease of about 50% in recoveries, addition of standard humic acid a decrease of about 20%. The capacity of GCB cartridges was determined with the breakthrough volume for 4-aminobenzoic acid at different concentrations to be 0.5–1% (w/w).     

An experimental method for testing the solvophobic theory by using graphitized carbon black in GC and LC

Summary The net solvent effect for several solute-solvent pairs has been calculated by using the solvophobic approach for describing the liquid chromatographic process. For the same solutes and solvents the net solvent effect has been experimentally measured by using graphitized carbon black columns in GC and HPLC. A comparison between the measured and calculated values made in terms of normalized free energy changes, indicates that the solvophobic theory is fairly adequate for predicting the sequence of solvent strength and provides a comprehensive explanation of the various interactions occurring in reversed-phase LC. A critical discussion of the deviations of the theory from the experimental data is also presented.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Adsorption of benzyl alcohol and 1-phenylethanol on graphitized thermal carbon black

The adsorption of benzyl alcohol and 1-phenylethanol on graphitized thermal carbon black at 300 K is investigated. Thermodynamic characteristics of the adsorption of conformers stable in the gas phase and in the adsorbed state are determined by a molecular statistics method. The geometry of the molecules is optimized using the MP2 and B3LYP methods with a 6-311++G(d,p) basis set. Using the PBE0/6-31G(d) method, it is established that, in the adsorption of benzyl alcohol, two types of interactions, CH…O and OH…π_GTCB, occur. It is shown that, in 1-phenylethanol, intramolecular interactions are maintained.     

Thermodynamic parameters of adsorption of isomeric chloronaphthalenes on graphitized thermal carbon black

Henry's constants and the heats of adsorption of isomeric chloronaphthalenes on graphitized thermal carbon black were calculated by the semiempirical molecular statistical method. The calculated data were compared with experimental results. The best agreement was achieved when corrections for the interaction of the Cl atom with the C atom of the adjacent benzene ring and the presence of other Cl atoms inortho-positions are introduced in calculations of the atom-atomic potential. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1484–1489, August, 1999.