F. Bruner

Graphitized carbon black: A unique adsorbent for gas chromatography and related techniques

SummaryThe properties of graphitized carbon blacks which have been exploited in gas chromatography and related techniques, are reviewed together with some of the many applications accomplished in the last twenty years. Graphitized carbon blacks are non-specific, non-porous adsorbents, characterized by a high surface homogeneity. These adsorbents can therefore be used in gas-solid chromatography even for the elution of polar compounds, though gas-liquid-solid chromatography is the main field of application. In fact, by changing the type and amount of liquid modifier, highly selective and efficient (packed or capillary) columns, tailored for the separation of very complex mixtures, can be prepared. Graphitized carbon blacks also possess hydrophobic properties so that they can be efficiently used for the trapping and the preconcentration of organic compounds contained in air and water samples.

Performance of graphitized carbon black cartridges in the extraction of some organic priority pollutants from water

Abstract The use of graphitized carbon black (GCB) cartridges for the extraction of organic pollutants (pesticides, phthalates, herbicides and polynuclear aromatic hydrocarbons) from water is discussed. Recovery tests carried out by spiking either the adsorbent or the water showed that nearly 100% recoveries can be obtained in most instances with 1 ml of a suitable eluent using 50 mg of GCB (Carbopack B). Examples of analyses of actual samples by gas chromatography—mass spectrometry are also shown. Levesl as low as 10 ppt can be determined.

Chromatographic properties and analytical applications of a low-surface-area graphitized carbon black

Abstract Retention data and heats of adsorption on a new low-surface-area graphitized carbon black have been determined and are compared with values for other adsorbents. The new adsorbent has been applied to gas chromatography of polar compounds such as alcohols, free fatty acids and phenols, and to environmental analyses.

Sample enrichment and GC-MS determination of herbicides in water

SummaryA sample enrichment method for herbicides from water, based on chromatographic extraction of organic compounds using graphitized carbon black is presented and its advantages and limits described. GC-MS and ECD are employed for qualitative analysis and quantitative determination.

Performance and use of wall-coated open tubular fused-silica columns with liquid-modified graphitized carbon black

Abstract The kinetic and thermodynamic changes induced in capillary columns with the internal area modified by a thin layer of graphitized carbon blacks are discussed and were tested experimentally. The selectivity due to the mechanism of gas—liquid—solid chromatography is greatly increased and the efficiency in terms of HETP is much improved at high linear gas velocities. This results in the possibility of obtaining faster analyses without the usual increase in operating temperature with respect to the gas—liquid technique. Examples of applications in practical analysis are given.

Graphite layer open tubular (GLOT) columns in gas chromatography and environmental analysis

SummaryThe preparation of graphite layer open tubular (GLOT) columns is described together with their application to the analysis of priority pollutants and polar compounds such as alcohols, free carboxylic acids, aliphatic amines and phenols at the sub-nanogram level.A specific application of GLOT columns is for the direct analysis of aqueous solutions avoiding solvent extraction procedures. Several chromatograms of critical separations are reported together with calibration curves. A study of the reproducibility of column preparation is reported in terms of the standard deviation of the capacity ratio and of the minimum HETP obtained.

New approach to the characterization of pyrolysis coal products by gas chromatography-mass spectrometry

Abstract A method for the characterization of coal thermal behaviour, based on gas chromatographic-mass spectrometric analysis of the pyrolysate, is presented. Twelve different coal samples, representative of the entire coal rank, were selected for this study. The pyrolysis products, obtained at 800°C, were first collected and then analysed in two GC-MS systems. The sampling apparatus consisted of three different traps in order to separate the products into three fractions on the basis of their volatility. The GC-MS analysis was also arranged according to this criterion. A packed column, coupled to a double-focusing magnetic mass spectrometer, was used for the volatile fractions of the pyrolysate and a capillary column, coupled to a quadrupole analyser, was employed for the analysis of the condensed fraction. Sampling and analysis procedures were carried out separately, thus allowing careful optimization of the strategy for the characterization of the pyrolysate. The condensate was analysed in the selected-ion monitoring mode for the determination of different classes of compounds. Some evaluations and comparisons, extrapolated from the results obtained, are presented.

PAHs, PCBs and Chlorinated Pesticides in Mediterraneal Coastal Sediments

Abstract Polynuclear aromatic hydrocarbons, chlorinated pesticides and polychlorobiphenyls have been identified and determined in coastal sediments by capillary gas chromatography-mass spectrometry after Soxhlet extraction with a petroleum ether-acetone mixture. Samples collected in three different areas along the Italian coast were analyzed and consistently different concentrations were found for the three locations. Possible sources of pollution have been investigated and identified.

Advances in the determination of volatile organic solvents and other organic pollutants by gas chromatography with thermal desorption sampling and injection

SummaryThe problem of the separation of 34 volatile organic chlorinated compounds is solved by using three different GC columns selected according to the needs of the particular separation required. The effect of water vapor contained as moisture in the trapped air on the retention of some characteristic compounds is studied. The influence of dead volumes on trap injection is also studied.

Calibration method for the gas chromatographic analysis of halocarbons in atmospheric samples using permeation tubes and an electron-capture detector

Abstract A method for calibrating the electron-capture detector for the analysis of halocarbons in atmospheric samples is presented. Permeation tubes are used as primary standards. The precision is evaluated under different operating conditions, and a standard deviation of 5% was the optimal. The difficulty of determining halocarbons present at very different concentrations is discussed.