Wilton R. Biggs

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.

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.

CHARACTERIZATION OF VANADIUM COMPOUNDS IN SELECTED CRUDES I. PORPHYRIN AND NON-PORPHYRIN SEPARATION

ABSTRACT We have applied size-exclusion chromatography (SEC-HPLC) and reversed-phase chromatography (RP-HPLC), with element specific detection, [Inductively coupled and direct current plasma atomic emission spectroscopy (ICP and DCP)], to selected crude oils –– Boscan, Beta, Morichal, Arabian Heavy, and Maya –– and their separated fractions. By these procedures, we have further characterized both the V porphyrin and the V non-porphyrin compounds. From the SEC-HPLC-ICP profiles of the heavy crude oils we found the V compounds generally have a bimodal distribution, with maxima at approx. 800 and 9000 polystyrene equivalent (PS) molecular weight (MW). Arabian Heavy, though, had relatively few of the small V compounds. The crude oils were separated into porphyrin and non-porphyrin fractions by methanol extraction. From the SEC-HPLC-ICP profiles of the porphyrin fraction, we Identified and quantitated the maximum at approx. MW 800 (PS) as being V porphyrins. The remaining V compounds are non-porphyrin.

HPLC analysis of the large polycyclic aromatic hydrocarbons in a diesel particulate

SummaryHigh performace liquid chromatography (HPLC) was used to separate the large polycyclic aromatic hydrocarbons in a diesel particulate extract. Identification of individual peaks was made using a photodiode array UV/visible detector to collect their absorbance spectra. Comparisons between standard compounds and the peaks were made using both retention times and spectra. Compounds of up to 10 rings were identified.

Planarity recognition of large polycyclic aromatic hydrocarbons by various octadecylsilica stationary phases in non-aqueous reversed-phase liquid chromatography

SummaryPlanarity recognition of polycyclic aromatic hydrocarbons has been investigated using bonded octadecyl stationary phases synthesized in different ways. Retention results indicate apparent differences among the functionalities of the stationary phases, a fact found useful for identifying the functionality of commercially available octadecylsilica (ODS) phases. Retention behevior can be explained by the slit-like structures of polymeric oDS phases, as evidenced by suspension13C NMR measurements.

Effect of column temperature on the retention of peropyrene-type polycyclic aromatic hydrocarbons on various chemically bonded stationary phases in reversed-phase liquid chromatography.

The effect of column temperature on the reversed-phase retention of polycyclic aromatic hydrocarbons has been investigated using various chemically bonded phases. Four solutes, coronene, tetrabenzo[a,cd,j,lm]perylene, tetrabenzo[a,cd,f,lm]perylene and benzo[lm]phenanthro[4,5,6-abcd]perylene, were used as the test probes. The temperature dependences of the retention are almost linear (the logarithm of capacity factor is proportional to the reciprocal of the column absolute temperature) with monomeric C18, monomeric C18 with endcapping and diphenyl bonded phases, while non-linear behaviour was observed with polymeric C18 phases. These differences in behaviour of the stationary phases are interpreted in terms of their structural differences.