John C. Fetzer

High molecular weight polycyclic aromatic hydrocarbons in hydrothermal petroleums from the Gulf of California and Northeast Pacific Ocean.

Hydrothermal petroleums and heavy tars have been analyzed for polycyclic aromatic hydrocarbons (PAH) with molecular weights greater than that of coronene (300 da). Samples from the hydrothermal systems in the Guaymas Basin (Gulf of California) and in the Escanaba Trough and Middle Valley (Northeastern Pacific) were analyzed by gas chromatography-mass spectrometry and high pressure liquid chromatography with diode-array absorbance detection. Mass spectra and fluorescence spectra were used to characterize the compounds. Several large PAHs with six and more rings were identified among the heavy PAH. Production routes via one-ring build-up and Scholl-condensation are proposed to explain the observed structures. The variations in PAH concentrations and distributions between samples from different locales are a consequence of the hydrothermal conditions of generation, migration, and post-depositional alteration.

Monitoring and characterization of polyaromatic compounds in the environment

This paper provides an overview of analytical techniques and instruments used to monitor and characterize polycyclic aromatic compounds (PACs) in the environment. The basic operating principles of various analytical approaches and systems are presented. The review deals specifically with spectroscopic methods, chromatographic and hyphenated techniques, and field monitoring devices. Emphasis is given to portable devices that can be used under field conditions. Specific examples of analytical techniques and instruments developed in the authorss laboratories will be discussed to illustrate the usefulness and potential of these approaches for environmental monitoring and characterization of PACs.

Retention behaviour of large polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography on a polymeric octadecylsilica stationary phase

Abstract Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and differential scanning calorimetry experiments were performed in order to study the retention mechanism in reversed-phase liquid chromatography for large polycyclic aromatic hydrocarbons. The effects of changing the mobile phase composition and column temperature were evaluated. The results suggest that a change in mobile phase composition from pure methanol to pure dichloromethane induces further non-planarity in non-planar solutes and also slightly changes the conformation of a polymeric octadecyl stationary phase. Conversely, a change to higher column temperatures drastically changes the structure of the stationary phase from solid-like to liquid-like, with only a small change of non-planar solutes to more non-planar conformations

The high-performance liquid chromatography of pero-pyrene-type polycyclic aromatic hydrocarbons

Abstract Various large polycyclic aromatic hydrocarbon ring structures of potential environmental and biological interest are synthesized and charaterized. These compounds are the used as standards in the development of analytical high-performance liquid chromatographic separations.

Eluation behaviour of planar and non-planar polycyclic aromatic hydrocarbons on various chemically bonded stationary phases in liquid chromatography

The elution behaviour of planar and non-planar polycyclic aromatic hydrocarbons has been studied on various stationary phases in reversed-phase and normal-phase liquid chromatography. The results show that the elution behaviours of the isomer sets which have distinctly different planarities such as triphenylene, triphenylmethane or o-terphenyl reflect the characteristics of the chemically bonded stationary phases. The phases studied included polymeric C18, monomeric C18 (with end capping), monomeric C18 (without end capping), triphenyl, naphthylethyl and pyrenylethyl phases.

Solvated structure-retention relationships of peropyrne-type polycyclic aromatic hydrocarbons

Abstract The peropyrene-type class of polycyclic aromatic hydrcarbons (PAHs) resulting from the zinc dust fusion of perinaphtone and benzanthrone, contains several member whose degree of planarity is highly dependent on the solvent in which the sample is dissolved. The reversed-phase behavior of these compounds is profoundly effected by the changes in planarity. The nature of, and changes in, the UV-VIS spectra of the PAHs could be used to qualitatively predict which isomers would posses anomalous retention behaviour.

Liquid chromatographic separation of all-carbon molecules C60 and C70 with multi-legged phenyl group bonded silica phases

Abstract The separation of C60 and C70 all-carbon compounds has been examined using new multi-legged phenyl group bonded silicas as the stationary phase in liquid chromatography. Two-legged biphenyl bonded silica gave the best separation because this phase offers the most suitable cavity-like structure to retain the C70 molecule, and this provides good separation between C60 and C70.

Molecular shape recognition capability of liquid-crystal bonded phases in reversed-phase high performance liquid chromatography

SummaryThe chromatographic retention behaviour of two liquidcrystal bonded phases have been evaluated using polycyclic aromatic hydrocarbons (PAHs) as the probe samples in reversed-phase high performance liquid chromatography (RP-HPLC). The results clearly indicate that these phases have better planarity and shape recognition capabilities than commercially-avaialble polymeric octadecylsilica (ODS) phases whose strong planarity and shape selectivities were found earlier. It can also be concluded from the chromatographic observations that the shape recognition capability of these phases is dependent on both mobile phase composition and column temperature, but that the effect of mobile phase and temperature on the shape selectivity work independently. The retention behaviour can be explained by changes in the phase structure with changes of eluent composition and temperature.

Elution behaviour of peropyrene-type polycyclic aromatic hydrocarbons in various chemically bonded stationary phases in reversed-phase liquid chromatography

The elution behaviour of polycyclic aromatic hydrocarbons (PAHs, 13 of the 16 U.S. Environmental Protection Agency priority pollutants and peropyrene types) was studied on several chemically bonded stationary phases (octadecylsilicas, di- and triphenylsilicas, naphthylethylsilica and pyrenylethylsilica) under reversed-phase conditions. The results showed that the elution order of peropyrene-type PAHs is highly dependent on the degree of planarity of the solute and on the orderlines of the bonded phases, whereas no definite differences were found in the retention behaviour of the 13 small PAHs on various stationary phases. The characteristics of all the stationary phases could be classified by statistical cluster analysis.

Vanadylporphyrins, indicators of kerogen breakdown and generation of petroleum

Abstract Attempts at understanding the transformation of organic material into fossil fuels often relies on biomarkers, organic compounds present in the geological record that can be related to naturally-occurring molecules from specific organisms. While porphyrins were the first biomarkers identified in fossil fuels, no significant use has been made of them in geochemical correlation studies. We believe that one limitation to their usage has been inaccurate models proposed for the fate of porphyrins during catagenesis. Using laboratory pyrolysis experiments we show that the changes observed in vanadylporphyrin distribution during catagenesis is due to increasing dilution of preexisting DPEP vanadylporphyrins by ETIO vanadylporphyrins released from kerogen. In conjunction with a quantitative expression describing the change in vanadylporphyrin distribution during maturation called the Porphyrin Maturity Parameter (PMP), a basis is now provided for the use of vanadylporphyrins as indicators of onset of petroleum generation.