Application of capillary supercritical fluid chromatography to the analysis of a middle distillate fuel

Summary The application of capillary supercritical fluid chromatography (SFC) to the analysis of a middle distillate fuel is described. Small diameter (50m i.d.) fused-silica capillary columns coated with crosslinked 50% phenyl polymethylphenyl siloxane provided high separation efficiency and good compatibility with flame ionization detection. High resolution separations of the chemical class fractions obtained by adsorption chromatography on alumina were obtained using carbon dioxide as the supercritical mobile phase and simple pressure programming techniques. In addition to the less polar fuel components, supercritical carbon dioxide allowed chromatography of the nitrogen-containing polycyclic aromatic hydrocarbon fraction and the hydroxylated polycyclic aromatic materials.     

Chromatographic chemical characterization of solvent refined coal I and II liquids for toxicological testing

Summary High resolution gas chromatography and gas chromatography/mass spectrometry were employed to determine the components in samples of solvent refined coal (SRC) II naphtha, middle distillate, heavy distillate, and fuel oil blend and SRC-I light oil, wash solvent, and process solvent in concentrations higher than approximately 0.5%. Quantitation was based on the addition of n-alkane internal standards and peak area response of a flame ionization detector with the use of fused silica and glass capillary columns coated with SE-52 and SF-96. The major differences in the SRC-I and II materials were the molecular weight ranges and sizes of the chemical components found in the products, an effect of the differences in the nominal boiling ranges of the materials. Alkanes, alkenes, hydroxylated aromatics, hydrogenated and polycyclic aromatic hydrocarbon ring systems, and alkylated derivatives of the above were found in greatest concentration in the unfractionated materials. Sulfur and nitrogen heteroatomic species were in greates concentration in the higher nominal boiling range materials. A major purpose of these investigations was to develop a method to obtain data on the composition of these complex sample matrices for use in designing studies for toxicological evaluation of these materials.     

Comparative chemical analysis of commercial creosotes and solvent refined coal-II materials by high resolution gas chromatography

The chemical composition of a commercially available creosote was compared to a direct coal liquefaction product, i.e., solvent refined coal-II fuel oil blend (SRC-II FOB) using high resolution gas chromatography (HRGC). In addition, hydrogenated products of these materials were studied. Samples were fractionated by chemical class on neutral alumina. Those fractions previously shown to be the most mutagenic and tumorigenic in laboratory bioassays of coal-derived materials were analyzed and compared by HRGC and gas chromatography/mass spectrometry (GC/MS). Individual components were tentatively identified and quantitated. Although similar chemical components were present in the creosote and SRC-II FOB fractions studied, the creosotes had higher concentrations of heavy molecular weight materials and a lower ratio of alkylated to parent polycyclic aromatic compounds than the coal liquefaction products. The creosote samples also had a significantly higher concentration of components which eluted in the polycyclic aromatic hydrocarbon (PAH) chemical class fraction. Amino-substituted PAH were present in both nonhydrogenated coal liquid and creosote materials. The creosote and SRC-II FOB crudes and nitrogen-containing polycyclic aromatic compound (NPAC) chemical class fractions expressed similar microbial mutagenicity. Based on chemical analysis data, the predicted tumorigenic potency of the creosote in laboratory bioassay systems would be equivalent to or greater than the SRC-II FOB.     

单壁碳纳米管+SE-30毛细管柱的制备研究及对多种物质的拆分

使用单壁碳纳米管(SWNTs)作气相色谱的固定相, 并用静态涂渍法在单壁碳纳米管内壁涂渍浓度不同的SE-30固定液. 为考察固定液浓度不同的几根毛细管柱的柱性能, 对多种物质进行了拆分, 并将该拆分结构与直接涂渍SE-30柱的毛细管柱性能进行对照. 实验结果表明: 键合了SWNTS再涂渍SE-30的毛细管柱较之直接涂渍SE-30的毛细管柱拆分效果有所改进, 但存在一定的拖尾现象. 此外, 前者对气体有较好的拆分效果, 且其效果随SE-30浓度按一定规律变化. 从分离性能来看, 键合了SWNTS再涂渍SE-30的固定相对气体的分离具有较好的效果.     

Studies of open tubular micro capillary liquid chromatography. 1. The development of open tubular micro capillary liquid chromatography

Micro capillary columns were successfully applied to liquid chromatography by employing the principles used in micro high performance liquid chromatography. Fundamental investigations on the use of capillary columns in LC were performed for the various column parameters. Good separations of five aromatic hydrocarbons and four kinds of phthalic esters were obtained on a 62 μm I.D. capillary column, coated with SE-30.     

Analysis of polycyclic aromatic compounds in the fly ash of an incineration plant for radioactive waste

Organic compounds adsorbed on fly ash from an incinerator for radioactive waste were investigated. Following Soxhlet extraction and concentration, analysis was performed by GC and GC/MS using high temperature silylated glass capillary columns coated with OV-1 and SE-54. Compound identification was based on retention data, relative detector responses, and mass spectra. Among other polycyclic aromatic compounds, series of gradually chlorinated PAHs containing four to seven aromatic rings were detected. For unequivocal identification, appropriate reference compounds were synthesized by chlorination of the corresponding parent PAHs.     

Study of a monolithic silica capillary column coated with poly(octadecyl methacrylate) for the reversed-phase liquid chromatographic separation of some polar and non-polar compounds

The performance of a monolithic silica capillary column coated with poly(octadecyl methacrylate) (ODM column) for the reversed-phase liquid chromatographic separation of some polar and non-polar compounds was studied, and the results were compared to those obtained by using a monolithic silica capillary column modified with octadecylsilyl-(N,N-diethylamino)silane (ODS column). Benzene and naphthalene derivatives, polycyclic aromatic hydrocarbons (PAHs), steroids, alkyl phthalates, and tocopherol homologues were used as test samples. In general, compounds with aromatic character, rigid and planar structures, and lower length-to-breadth ratios (more compacted structures) seem to have more preference for the polymer coated stationary phase (ODM). Compounds with acidic character have also a higher retention on ODM columns because of the presence of ester groups in the stationary phase. The polymer coated column allowed the separation of some PAHs, alkyl phthalates, steroids, and of beta- and gamma-tocopherol isomers which cannot be separated under the same conditions on ODS columns, while keeping similar column efficiency. These results allowed to suggest ODM columns as a good alternative to conventional ODS columns for reversed-phase liquid chromatography.     

C_5馏分及其羰化产物的毛细管气相色谱分析

石油裂解副产物C5馏分及其羰化产物是成分较为复杂的混合物,尤其是C5馏分中1,3-环戊二烯和顺-1,3-戊二烯的物性更为接近。用SE－54弹性石英毛细管柱和角鲨烷玻璃毛细管柱分别对C5馏分及其羰化产物进行了分析,使各组分达到了很好的分离。     

Automated capillary gas chromatographic analysis of pesticide residues in food

A method for multiresidue pesticide analysis in food is described. After a conventional clean-up, gas chromatographic analysis is performed in a gas chromatograph equipped with two fused-silica capillary columns coated with methylsilicone SP 2100 and methylphenylsilicone OV-17. The effluent from each column is split to electron-capture and nitrogen-phosphorus detectors, which are connected to a dual channel integrator. Therefore, from each gas chromatographic run parallel records of signals from the two detectors are obtained. Calibration of the system is carried out for the SP 2100 column with three test mixtures covering all pesticides. Additionally, four internal standards are included, two responding to the electron-capture detector and the other two to the nitrogen-phosphorus detector. Automated analysis is performed with test mixtures and food samples on the SP 2100 column overnight as a screening procedure. After selection of positive samples a confirmatory test and quantitation are carried out manually applying appropriate test mixtures according to the results of the screening runs.     

Clean-up and analysis of carbazole and acridine type polycyclic aromatic nitrogen heterocyclics in complex sample matrices

A HPLC method for the analysis of polycyclic aromatic nitrogen heterocyclics (PANHs) in complex sample matrices is presented. It isolated and separated carbazole and acridine type PANHs with an absolute recovery of between 79–98%. Open column chromatography is used as an initial step to isolate a PANH fraction. By applying normal-phase liquid chromatography using a dimethylaminopropyl silica stationary phase and utilising back-flush technique it was possible to separate the PANH fraction into two fractions containing acridine type and carbazole type PANHs, respectively. The method applied on a sample of solvent refined coal heavy distillate (SRC II HD). A number of 3–5 ring acridines and carbazoles were identified with GC–electron impact MS and quantified with GC–nitrogen–phosphorous detection. Polycyclic aromatic hydrocarbons (PAHs) were determined in the SRC II HD sample by automated on-line clean-up and analysis of the obtained PAH fraction with coupled LC–GC–flame ionization detection. There was no overlap between the PANH and the PAH fractions with this method, and carbazoles and acridines were efficiently separated.     

The preparation of immobilized stationary phase fused silica capillary columns with OV-1701-vinyl deactivation

A new simplified method was developed for the preparation of immobilized stationary phase fused silica capillary columns coated with OV-1-vinyl, SE-54, and OV-1701-vinyl. This methodology includes the application of the moderately polar stationary phase OV-1701-vinyl as a surface deactivation agent that may also participate in the dicumyl peroxide initiated free radical immobilization process. Practical details of the procedure are presented and applications of the laboratory-produced columns are illustrated with capillary gas chromatographic separations of standard mixtures. Possible contributions of the OV-1701-vinyl deactivation layer to both crosslinking and surface bonding in the immobilization process are discussed.     

Multidimensional Gas Chromatography–Mass Spectrometry Method for Fingerprinting Polycyclic Aromatic Hydrocarbons and Their Alkyl-Homologs in Crude Oil

The composition of polycyclic aromatic hydrocarbons in crude oil is usually too complex to use standard capillary gas chromatography to separate all of the components. In this study, a multidimensional gas chromatography–mass spectrometry (GC-MS) technique was used to analyze polycyclic aromatic hydrocarbon fractions of crude oil collected from the Dongying oil field in the Bohai Sea. A DB-17MS column (30?m?×?0.25?mm?×?0.25?µm) was used as a prefractionating column and only selected heart-cuts were transferred to the second chromatographic dimension (HP-5MS, 15?m?×?0.25?mm?×?0.25?µm) by a pressure-adjusted continual flow-type switching device for quantification of the polycyclic aromatic hydrocarbons. The chromatographic elements and parameters, such as detector selection and column combinations, were optimized. Naphthalene, phenanthrene, fluorene, dibenzothiophene, chrysene, and their C₁–C₄ alkyl homologs were identified. The profile of the polycyclic aromatic hydrocarbons obtained using the multidimensional GC-MS method was compared with the results obtained by traditional one-dimensional GC-MS.     

Comprehensive two-dimensional gas chromatography for enhanced analysis of naphthas: new column combination involving permethylated cyclodextrin in the second dimension

A new column association using comprehensive two-dimensional gas chromatography for the detailed molecular analysis of hydrocarbon mixtures is reported in this paper. In order to compare the impact of two different secondary columns, a novel column combination relying on a GC x 2GC system was used. This system is based on a non-polar first column (PONA) combined with both a permethylated beta-cyclodextrin (beta-Dex 120) stationary phase and a polysilphenylensiloxane (BPX 50) in the second dimension. Compared to BPX 50 stationary phase, the implementation of beta-cyclodextrin columns as the second dimension was found to improve the resolution between paraffins and naphthenes in the naphtha range but not in the middle distillate range. Attempts to improve the results and to understand the interaction mechanism remained unsuccessful. Therefore, the benefits of the beta-Dex 120-column are only demonstrated on heavy naphtha cut for the quantitation of hydrocarbons.     

Glass-capillary chromatography in medical research

Summary This paper deals with our experiences with glass-capillary chromatography in medical research. We reported earlier about chromatography of fatty acid methyl esters on a 50 m glass capillary, coated with FFAP. Now we have experimented with a 50 m Silar 10 C column, which gives even better results. The analysis of bile acids on 20 m columns, coated with OV-17, SE-54 or Silar-10 C yields good chromatograms and resolves the main bile acids by base line separation. Further, we are able to report the chromatography of steroid hormones extracted from human urine on a 50 m glass capillary coated with OV-101. Preliminary assessment can be made of the chromatography of the 20 major amino acids after butylation and acetylation on a 50 m Silar-10 C column. As an example of the analysis of vitamins we have chosen the chromatography of nicotinic acid and its isomer. In summary, we are able to show the wide variety of applications of the glass capillary column in medical research.     

Retention system, thermodynamic properties and structure correlations of environmental analytes

Summary A composite chromatographic retention index system has been developed for identifying polycyclic aromatic hydrocarbons, polychlorinated biphenyls and polychlorinated pesticides. When retention indices and thermodynamic data of polycyclic aromatic hydrocarbons on 5% phenylmethylsiloxane stationary phase were compared with those obtained on polydimethylsiloxane a correlation was found between retention and electronic properties. Determination and quantitation of individual contaminants in water and sediment samples from Lake Mecoacán were achieved by capillary gas chromatography with flame ionization and electrocapture detection.     

Fast headspace analysis with short microcapillary columns

Summary A new method of analysis using headspace gas chromatography with microcapillary columns is proposed. Small diameter (50 μm I.D.) fused-silica capillary columns with non-extractable SE-54 and PS-255 polysiloxane stationary phases were used for the analysis of low boiling organic compounds. The small diameter columns possess the usual very high efficiency so that the method can be employed for the headspace analysis of complex mixtures. The use of short microcolumns reduces the analysis times in comparison to conventional capillary columns. Good performances were obtained in the analysis of volatile compounds in some lemon essential oil, perfumes, and water samples.     

Capillary Column Gas Chromatography of Environmental Polycyclic Aromatic Compounds

Abstract

The methodologies are described for isolating clean fractions of polycyclic aromatic compounds from diverse environmental samples such as air particulate matter, sediments, and fish tissue. The common step in all procedures is the separation of the polycyclic aromatic compound fraction into well-defined chemical classes by adsorption chromatography on an alumina column. These procedures greatly facilitate the detailed characterization of the polycyclic aromatic hydrocarbons, sulfur heterocycles, and nitrogen heterocycles by capillary column gas chromatography.     

Single fiber-in-capillary annular column for gas chromatographic separation

A method for preparation of a stationary phase-adjustable column with in-column stationary phase-coated fused-silica fiber annular column was successfully developed. The surface of a 0.12 mm o.d. bare optical fiber was first coated with a stationary phase and then inserted into a fused-silica capillary (non-coated or coated) as an annular column for gas chromatographic study. The optical fiber and capillary were coated with polydimethylsiloxane (SE-30) and polyethylene glycol 20M (PEG-20M) as nonpolar and polar stationary phases, respectively. Among the investigated annular and open tubular columns, the PEG-20M-coated fiber-in-PEG-20M-coated capillary annular column showed the highest column efficiency with a minimum plate height of 0.35 mm and an optimum gas velocity of 25 cm/s. When a SE-30/PEG-20M-coated fiber-in-uncoated capillary annular column was applied to separate a 9-component complex mixture, the total analysis time was 5.3 min and the column length was 12 m. By contrast, when a SE-30-coated fiber-in-PEG-20M-coated capillary annular column was used to separate the same 9-component mixture, the analysis time was reduced to 3.5 min and the column length was shortened by half to 6 m. Our results show that the stationary phase-coated fiber-in-stationary phase-coated capillary annular column is a better choice for gas chromatographic separation as it is more efficient and flexible. In addition, the proposed annular column design provides flexibility in using two or even more types of stationary phases to achieve optimal analytical separation.     

Effect of column diameter on efficiency in capillary supercritical fluid chromatography

Fused silica capillary columns with internal diameters from 100 to 25 μm were coated with SE-54 and evaluated under supercritical fluid chromatographic conditions using carbon dioxide as mobile phase. Experimental results compared well with theoretical predictions. At ten times the optimum mobile phase velocity and for a capacity factor, k of 3, efficiencies of 2300 to 5600 plates m^?1 were obtained for column diameters of 100 to 25 μm, respectively.     

Gas chromatographic determination of chlorinated phenols in the form of various derivatives

Derivatization of chlorophenols prior to gas chromatographic analysis resulted in a significant improvement of their chromatographic behaviour. Chlorophenols in the form of anisoles, acetates, and pentafluorobenzyl ethers were separated either on a HP-1 wide-bore capillary column or on a capillary column coated with a film of SE-54. Due to an enhancement of the poor electron-capture detection response of mono- and dichlorophenols, pentafluorobenzylation made it possible to determine trace amounts in spiked water. Moreover, simultaneous analysis of phenoxyalkanoic acids was accomplished under the same conditions.