Filippo Mangani

Light hydrocarbons in hydrothermal and magmatic fumaroles: hints of catalytic and thermal reactions

Volcanic gaseous mixtures emitted from active volcanoes frequently show variable amounts of saturated (alkanes), unsaturated (alkenes) and aromatic volatile hydrocarbons. Three major patterns of distributions can be recognized, apparently related to the chemical-physical environment of formation of the gas exhalations: alkane-rich, low-temperature gas emissions from recently active volcanic areas; aromatic-rich hydrothermal manifestations; and alkene-rich, ‘magmatic’ fumaroles on active volcanoes. Thermodynamic data, together with theoretical and practical findings from the petroleum industry, point to two main types of reactions occurring in these volcanic environments: cracking and reforming. Cracking processes, mainly caused by thermal effects, occur when hydrocarbon-bearing hydrothermal fluids enter and mix with a hot and dry, rapidly rising magmatic gas phase. The most probable products are light alkenes with carbon numbers decreasing with increasing reaction temperatures. The presence of aromatic species in hydrothermal fluids can be linked to reforming processes, catalysed by several possible agents, such as smectites and zeolites, generally present in the hydrothermally altered volcanic terranes, and facilitated by long residence times in a hydrothermal envelope.

Monitoring of active but quiescent volcanoes using light hydrocarbon distribution in volcanic gases: the results of 4 years of discontinuous monitoring in the Campi Flegrei (Italy)

During the period from January 1991 to January 1994, the 10-yr geochemical monitoring in the Campi Flegrei (Southern Italy), usually performed using the inorganic gas fraction, was implemented by discontinuous monitoring of the hydrocarbon gas fraction. The measured compositions have revealed the presence of significant amounts of at least 11 hydrocarbon species, related to alkane, alkene, and aromatic classes. Thermodynamic calculations showed the possible existence of partially independent equilibria within the C1/C2/C3 and C1/C2/C3/C4 alkane systems, as well as among alkene/alkane pairs at redox conditions controlled by the geothermal (FeO/Fe1,5O) redox buffer system, at temperatures between 200 and 400°C and PH2O controlled by the presence of a saline brine. Unlike the constancy of the measured and calculated ‘inorganic’ temperature, equilibrium temperature based on organic species has displayed fluctuations and a significant increase starting from the second half of 1993. According to their apparent correlation with other independent observations, such as the measured increases of vapor fraction, H2S/CO2 and H2/N2 ratios on the monitored fumarole in addition to a general increase of dissolved CO2 in the Campi Flegrei groundwaters, the observed variations of the organic parameters were interpreted as the result of a general increase in acid-bearing gas flux throughout the re-equilibration zone.

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.

Liquid chromatographic-mass spectrometric determination of phenolic compounds using a capillary-scale particle beam interface.

A capillary-scale particle beam interface was used to detect 18 phenolic compounds in red wine samples. This technique allows reproducible, library searchable electron ionization spectra at only 1 microliter/min mobile phase flow-rate for a sensitive detection of the analytes in complex matrices. The method makes use of a narrow bore, reversed-phase packed capillary column for sample separation. Detection limits were in the low picogram range for most compounds. Sensitivity and response linearity were evaluated for eight phenolic acids, which are often encountered in red wines. The phenolic compound composition was outlined in two red wines obtained using different aging processes.

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.

A simple approach for coupling liquid chromatography and electron ionization mass spectrometry

A miniaturized, aerosol based interface for directly coupling a liquid chromatograph with a mass spectrometer is presented. The interface is entirely within the electron ionization (EI) source of the mass spectrometer and no additional, external devices are needed. This simple and effective approach exploits micro-flow nebulization technology providing a new interface suitable for a variety of applications of environmental and biological interest. The new interface provides necessary linearity, ruggedness, sensitivity, and reproducibility of response for trace level analysis, and readily interpretable mass spectra for unambiguous identification of unknown compounds of small to medium molecular weight.

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.

Evaluation of the working conditions of light adsorbents and their use as sampling material for the GC analysis of organic air pollutants in work areas

SummaryThe use of traps containing graphitized carbon black for the collection and pre-analysis of atmospheric pollutants in industrial areas is presented. The working conditions, in terms of trapping capability and effectiveness of release by thermal desorption are discussed. Some practical applications are also given.

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.

New materials and packing techniques for micro-HPLC packed capillary columns

SummaryPlastic tubing of polyetheretherketone (PEEK) is used for the preparation of HPLC packed capillary columns. The polymer is rigid but not fragile, has great resistance to chemical and physical agents and comes in standard 1/16″ O.D. These features can extend the column lifetime and facilitate the overall employment of HPLC capillary columns. Serial connection of short columns is also possible with no increase in dead volume. A new, rapid and effective packing method has been developed to be compatible with the characteristics of the material. Several C8 and C18 columns have been prepared and tested and some applications are shown.