Retention of diphenyls,terphenyls, phenylalkanes and fluorene on graphitized thermal carbon black

Summary This paper defines values of retention volumes for zero surface coverage (Henry's constant) at different temperatures, retention indices and variations of the internal energy (differential heats of adsorption) of diphenyl and its alkyl derivatives, terphenyls, diphenylmethane, triphenylmethane, diphenylethanes and fluorene on graphitized thermal carbon black (GTCB). Adsorption on GTCB takes place in accordance with the geometry of these molecules, the strongest adsorption being observed for para-terphenyl with least inhibited internal rotation of the molecule, while the weakest adsorption occurs for 2,6,2,6-tetramethyldiphenyl with the most inhibited internal rotation of the molecules. The flat molecules of fluorene are adsorbed on GTCB more readily than the nonflat molecules of diphenylmethane.     

Gas chromatography-mass spectrometry in the study of the adsorption of sulfur-containing amino acids on graphitized thermal carbon black

Summary Gas chromatographic — mass spectrometric study of the trifluoroacetyl-methyl esters of sulfur- and hydroxyl-containing amino acids such as methionine, cysteine, D-,-dimethylcysteine (D-penicillamine), serine, and threonine was carried out. Sterling hydrogen treated graphitized thermal carbon black (HTGTCB) was used as the adsorbent. The Henry's constants, and the initial differential adsorption heats of these amino acid derivatives were determined on the HTGTCB surface by gas chromatography.Introduction of two methyl groups into the -position of a cysteine molecule (,-dimethylcysteine) stimulates the intramolecular nonvalent interactions increasing the internal rotation barriers in the molecule. This is revealed in the sharply reduced retention of the ,-dimethylcysteine derivative on the HTGTCB surface (as compared to the cysteine derivative) and it also influences the fragmentation pathways under electron impact.Deceased.     

Separation of isomers of saturated polycyclic hydrocarbons in packed capillary columns with graphitized thermal carbon black

Summary Using the example of perhydrophenanthrene, perhydroanthracene and cyclopentanodecalin isomers a possibility is shown to use packed capillary columns containing graphitized thermal carbon black for a complete separation of high-boiling mixtures of polycyclic saturated hydrocarbon isomers in accordance with the geometric structure of their molecules.     

基于石墨化炭黑预涂覆技术的色谱柱制备和性能评价

采用石墨化炭黑(GCB)预涂覆技术对白酒分析专用色谱柱(LZP-930)的制备方法进行了优化,详细考察了所制备的色谱柱(LZP-930G)的性能参数,并对LZP-930G色谱柱的保留行为进行了评价,探讨了GCB对LZP-930G色谱柱性能的影响。研究发现,LZP-930G色谱柱的柱效、惰性、稳定性和极性均得到了明显提高,从而改善了酸类和醇类组分的分离选择性和色谱峰峰形,实现了白酒中53种易挥发和半挥发性微量组分的同时分离,且各组分的保留时间和峰面积的相对标准偏差分别小于0.63%和4.51%(n=5)。表明GCB预涂覆技术能够用于高性能白酒分析色谱柱的制备方法。     

Retention of some ring-substituted aniline derivatives by porous graphitized carbon. Dependence on physico-chemical parameters

Summary The retention characteristics of 22 aniline derivatives were determined on a porous, graphitized-carbon column in unbuffered acetonitrile-water and methanol-water mixtures. Each aniline derivative gave symmetrical peaks in each eluent without buffers. Good linear correlations were found between the log k and the concentration of the organic component in the eluent. The slope and intercept values differed according to the type of organic modifier and the charcter, number and position of substituents, indicating the different selectivities of methanol and acetonitrile and the good separating power of the column. Multivariate mathematical-statistical calculations proved that the retention of ring-substituted aniline derivatives is mainly governed by electronic parameters and the hydrogen acceptor capacity of substituents.     

Thermodynamic parameters of adsorption of adamantane and its derivatives on graphitized thermal carbon black

The adsorption equilibrium constants for adamantane, 1-fluoro-, 1-chloro-, 1,3-difluoro-, 1,3-dichloro-, 1,3-dibromo-, and 1-hydroxyadamantane, and methyl 1-adamantyl ketone were determined by gas chromatography. The results were compared with molecular statistical calculations based on the known atomic-atomic potentials of the interaction of atoms of the sorbate molecule with the C atom of graphitized thermal carbon black (GTCB). The experimental adsorption heats exceed the calculated values by 3-10 kJ mol^-1. The reasons for this divergence are discussed. The changes in the adsorption entropy show that the molecules of the studied compounds form a layer of the ideal dimeric gas on the GTCB surface upon adsorption.     

Description of adsorption of haloalkanes and haloarenes on graphitized thermal carbon black by means of the model of an ideal two-dimensional gas

The standard entropies theoretically calculated for 40 haloalkanes and haloarenes adsorbed on graphitized thermal carbon black were compared with those determined from the adsorption-chromatographic data. It was found that a molecular model of an ideal two-dimensional gas is a sufficiently good approximation in all the cases. For a number of systems, agreement can be improved by taking into account the vibrations of the center of the molecular mass relative to the surface. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2173–2176, December, 1997.     

Molecular structure and retention behaviour of some polycyclic aromatic and perhydroaromatic hydrocarbons on graphitized carbon black

Summary On efficient glass capillary columns packed with graphitized thermal carbon black (GTCB) the stereoisomers of aromatic and saturated tricyclic hydrocarbons are completely separated and identified. The Henry's adsorption constants of the individual isomers were determined from mixtures at different temperatures. Five isomers of perhydroanthracene, five isomers of perhydrofluorene, two isomers of perhydrophenalene, four isomers of perhydroacenaphthene, as well as phenalene, dihydrophenalene, acenaphthene and acenaphthylene were investigated. The increase of the hydrogenization degree of unsaturated tricyclic hydrocarbons reduces the retention. Among the saturated tricyclic isomers the retention becomes shorter with the larger bending of the molecules, i.e. from the molecule having more equatorial bonds to the molecules having more axial connections. The experimentally determined Henry's constants were qualitatively compared with the structure of the separated molecules.     

Structure-retention correlations of hydrocarbons in GLC and GSC alkenylbenzenes

Summary For the study of relationships between retention behaviour and molecular structure in GLC and GSC the retention indices of alkenylbenzenes with 2–6 carbon atoms in a straight or branched side chain and of isotopological alkylbenzenes were determined on capillary columns coated with OV-1 and Ucon LB and on a micropacked column filled with graphitized thermal carbon black. From the values obtained index differences corresponding to the increments of the double bond in the side chain were derived. These differences depend significantly on the structure of the side chain and of the position of the double bond. In the case of 1-phenyl-1-alkenes the double bond close to the aromatic ring gives rise to an increase of retention values, especially for the trans-isomers, causing remarkable retention differences between the cis and transisomers. The alkenylbenzenes which exhibit a terminal double bond are less strongly retained than the isotopological alkylbenzenes. Partly presented on the 15th International Symposium on Chromatography 1984 in Nürnberg.     

A comparative study of biochar,multiwalled carbon nanotubes and graphitized carbon black as QuEChERS absorbents for the rapid determination of six triazole fungicides by UPLC-MS/MS

A rapid, effective and sensitive method to quantitatively determine six fungicide residue was developed using ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC–MS/MS). The target compounds were extracted by using acetonitrile and the sorbent used for clean-up in this modified QuEChERS analytical method were biochar, multiwalled carbon nanotubes (MWCNT) and graphitized carbon black (GCB). Results indicated that the MWCNT (10 mg) was the most effective sorbent in removing pigment. This method was validated on spinach, tomato, cucumber, celery, lettuce, rape, pakchoi, romaine lettuce and eggplant matrices spiked at three concentration levels of 0.01, 0.1 and 1 mg kg^?1. It exhibited recoveries between 73.1% and 118.2% with RSD values below 20%. Matrix-matched calibrations were performed with the coefficients of determination >0.9901 between concentration levels of 0.01–1 mg kg^?1. The limit of quantity (LOQ) for six pesticides ranged from 0.0036 to 0.011 mg kg^?1. The developed method was satisfactorily applied to determine pesticide residues in market vegetable samples.     

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.     

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

Summary A new graphitized carbon black (Carbograph 5) with a specific surface area (560 m² g⁻¹) greater than those of commerically available graphitized carbons was studied by gas chromatography to determine the enthalpy, entropy, and free energy of adsorption of a series of alkanes (C₂−C₆). The adsorption properties were also investigated by considering changes in the isosteric heats and entropies of adsorption when a nonpolar stationary phase (squalane) was added to the adsorbent. The data obtained are discussed and compared with literature values for other graphitized carbon blacks.     

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.     

Application of high‐surface‐area graphitized carbon black with primary secondary amine as an alternative quick,easy, cheap,effective, rugged,and safe cleanup material for pesticide multi‐residue analysis in spinach

A multi‐residue method has been developed and validated to determine 46 pesticides in spinach using liquid chromatography tandem mass spectrometry. The method is based on modified quick, easy, cheap, effective, rugged, and safe sample preparation, where high‐surface‐area graphitized carbon black was used first as sorbent material in the dispersive solid‐phase extraction. The method was compared with the quick, easy, cheap, effective, rugged, and safe method. The morphology, surface area, pore size, and pore volume of the sorbent was determined. The results obtained show that the sorbent consists of high surface area (233 m²/g) and large pore volume (1.5 cm³/g). The calibration curve correlation coefficient (R²) of the method was at least 0.99. The average recoveries ranged from 74 to 116%, and limits of detection and quantification from 0.0001 to 0.002 mg/kg and from 0.0002 to 0.005 mg/kg, respectively. Using the method, the pesticides exhibited low matrix effect (< 20%), except for nicosulfuron (29.86%), methomyl (26.77%), and flufenoxuron (24.65%). The method showed better potential to remove pigments than the quick, easy, cheap, effective, rugged, and safe method. It is demonstrated that the proposed method could be useful alternative for sample preparation of spinach and other matrices in future.     

甲烷在石墨化热解碳黑和活性炭上的吸附

为研究影响碳基吸附剂吸附超临界温度气体的主要因素,选择石墨化热解碳黑BP280和Ajax活性炭,分析超临界温度高压甲烷在其上的吸附平衡。应用容积法,在压力0~20.5 MPa、温度253 K~313 K测定甲烷的吸附平衡数据,并由等量吸附线标绘和亨利定律常数确定等量吸附热。引入通用吸附等温方程,再由方程的Langmuir标绘确定最大吸附容量,进而通过方程的线性化计算吸附平衡态中甲烷分子的作用能。结果表明,甲烷在两种吸附剂上的最大吸附容量均随温度而变化,并都小于液态甲烷的密度;甲烷在碳黑和活性炭上的等量吸附热分别为11.9 kJ/mol~12.5 kJ/mol和17.5 kJ/mol~22.5 kJ/mol,体现了两种吸附剂不同的表面能量分布;甲烷分子间作用能随吸附量的变化特点反映了超临界温度甲烷以类似于压缩气体状态聚集的特点和吸附剂结构上的差异。碳基吸附剂的比表面积和微孔容积是影响其储存甲烷容量的重要因素。     

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.     

Use of principal component analysis for investigation of factors affecting retention behaviour of ceramides on porous graphitized carbon column

Summary The potentiality of a porous graphitized carbon stationary phase was assessed for ceramide analysis in nonaqueous reversed phase chromatography with an evaporative light scattering detection. The influence of the nature of the mobile phase was first performed under isoeluotropic isocratic conditions. Eight mobile phase compositions in the presence or absence of triethylamine/formic acid were tested with a set of structurally relevant ceramides. Values obtained under these conditions for the peak heights, retention factors, plate numbers, asymmetry factors, relative retentions and Time-Corrected Calibrated Normalised Resolution Product were analysed by Principal Component Analysis. Principal Component Analysis was effective in attributing relationships between the chromatographic behaviour and analytical conditions. The relationship between the increase of the detector response and the presence of triethylamine/formic acid has been confirmed, and the main change of selectivity has been attributed to interactions provided by the weak solvent of the mobile phase. These conclusions have allowed the development of gradient conditions for the analysis of complex ceramide mixtures on porous graphitized carbon column.     

Adsorption of n-alkanes on a graphitized carbon black and its activation products in dry air

Summary Adsorption of n-alkanes (n-heptane to n-decane) on a graphitized carbon black and its activation products in dry air was carried out by a gas chromatographic technique. Adsorption runs were performed at finite surface coverage, to obtain the surface area and the London component of the surface free energy of the solids from the adsorption isotherms. On the other hand, the adsorption of n-alkanes carried out at zero surface coverage gave the differential heats of adsorption. The results show that, after the activation in dry air of the graphitized carbon black used, the surface area has a linear relationship with the degree of activation, whereas the surface heterogeneity changes in a parabolic fashion.     

Evaluation of graphitized glass capillary columns

The performance of graphitized glass capillary columns obtained by precoating the inner glass walls with graphitized carbon black has been evaluated. It has been shown that according to the amount of stationary phase coated such columns can operate in gas–liquid-solid chromatography and in gas–liquid chromatography so that tailor-made columns for specific separations can be prepared. The versatility of these columns is shown in the separation of various mixtures (terpenes, pesticides, isomeric species and others) of analytical importance.