Petroleum individual compound analysis

In the selection of a microbial system and bioremediation method, some examination of the degradation pathway is necessary. At a minimum, the final degradation products must be tested for toxicity and other regulatory demands for closure. Recent advances in the study of microbial metabolism of xenobiotics have identified potentially toxic intermediate products (Singleton, 1994). A regulatory agency sets treatment objectives for site remediation, and process analysis must determine whether bioremediation can meet these site objectives. Specific treatment objectives for some individual compounds have been established. In other cases total petroleum hydrocarbons total benzene, toluene, ethyl benzene, and xylene (BTEX) or total polynuclear aromatics objectives are set, while in yet others, a toxicology risk assessment must be performed. 

The results of chemical characterisation were not very consistent. It was discussed to prepare standard solutions with known amounts of compounds for quantitative analyses. A question was also raised if the functional groups in pyrolysis oil should be analysed analogously with petroleum residues instead of individual compounds, as by quantitative C-NMR. The amount of PAH (polyaromatic hydrocarbons) was extremely high for one pyrolysis oil, and it was discussed that more attention should be paid to the analysis of toxic compounds in the oils. The oil producer commented later that the high PAH may be due to contamination of other fuel and this will be checked. 

Recent advances in isotope analysis include the ability to analyse isotopically smaller proportions of individual compounds by the use of more sensitive online isotope ratio mass spectrometers (cf. Merritt Hayes 1994 Merritt et al. 1994) and stable carbon isotope determination of individual n-alkanes, isoprenoids and biomarkers in petroleums is now a standard tool. Despite early work on collection of chromato-graphically separated individual n-alkanes followed by combustion and isotope determination (Welte 1969) it was for a number of years impossible to analyse isotopically long chained alkanes with the same comfort and ease as the... 

Although the focus of many tests is analysis of the hydrocarbon constituents of naphtha and other petroleum fractions, heteroatoms compounds that contain sulfur and nitrogen atoms cannot be ignored, and methods for their determination are available. The combination of gas chromatography with element-selective detection gives information about the distribution of the element. In addition, many individual heteroatomic compounds can be determined. 

Carbon isotopic composition of individual biomarkers in gilsonites (Utah). In Compound-specific Analysis in Biogeochemistry and Petroleum Research (eds. M.Schoell and J. M. Hayes). Org. Geochem. 21, 673-683. 

Crude petroleum and the products obtained therefrom contain a variety of compounds, usually but not always hydrocarbons. As the number of carbon atoms in, for example, the paraffin series increases, the complexity of petroleum mixtures also rapidly increases. Consequently, detailed analysis of the individual constituents of the higher boiling fractions becomes increasingly difficult, if not impossible. 

Several studies have examined the total PAH content, the relative content of individual parent PAH compounds, that is, parent compound distributions (PCDs), and the alkyl homologue distributions (AHDs) of PAHs from extracts of marine sediments (1-9). The analytical methods used in these studies were generally complex and lengthy, and consisted of an extraction, an isolation of the PAH material (by either complex formation or chromatographic separation), and an analysis. Based on comparisons of PCDs and AHDs of the sediment samples with those of samples from known origins (e.g., petroleum, combustion products), these studies discussed the origins of PAH compounds found in sediments. 

In response to the oil spill identification need and specific site investigation needs, attention has focused on the development of flexible, tiered analytical approaches, which facilitate the detailed compositional analysis by GC-MS, GC-FID, and other analytical techniques that quantitatively determine a broad range of individual petroleum hydrocarbons. A variety of diagnostic ratios, especially ratios of PAH and biomarker compounds, for interpreting chemical data from oil spills have been proposed. 

A detailed analysis of individual sulphur compounds in oil is provided by Rail et al. (1972). In marine samples S-containing petroleum components such as benzothiophene, dibenzothiophene, naphthobenzothiophene, and their alkyl derivatives were obtained by Warner (1975) together with aromatic hydrocarbons. Alterations in the composition of S-compounds in crude oils exposed to the sea surface were analyzed by Utashiro and Hatsuo (1977). 

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