OIL SPILL SCIENCE chapter 5 – introduction to oil chemical analysis

OIL SPILL SCIENCE chapter 5 – introduction to oil chemical analysis OIL SPILL SCIENCE chapter 5 – introduction to oil chemical analysis OIL SPILL SCIENCE chapter 5 – introduction to oil chemical analysis OIL SPILL SCIENCE chapter 5 – introduction to oil chemical analysis OIL SPILL SCIENCE chapter 5 – introduction to oil chemical analysis

Chapter Introduction to Oil Chemical Analysis Merv Fingas Chapter Outline 5.1 Introduction 87 5.2 Sampling and Laboratory 87 Analysis 5.3 Chromatography 89 5.4 Identification and Forensic 96 Analysis 5.5 Field Analysis 107 5.1 INTRODUCTION An important part of the field of oil spill control is the analysis of oil in various media Oil analytical techniques are a necessary part of the scientific, environmental, and engineering aspects of oil spills.1-4 Analytical techniques are used extensively in environmental assessments of fate and effects Laboratory analysis can provide information to help identify an oil if its source is unknown or what its sources might be With a sample of the source oil, the degree of weathering and the amount of evaporation or biodegradation can be determined for the spilled oil Through laboratory analysis, the more toxic compounds in the oil can be measured, and the relative composition of the oil at various stages of the spill can be determined This is valuable information to have as the spill progresses In nonspill situations, analytical techniques are used extensively to measure the oil content of soil and water for environmental quality purposes Many jurisdictions have standards on the petroleum content of waters and soils for various uses In addition, many laws exist for the maximum oil content in soils Soils must often be removed for treatment before lands can be transferred from one owner to another 5.2 SAMPLING AND LABORATORY ANALYSIS Taking a sample of oil and then transporting it to a laboratory for subsequent analysis is common practice While there are many procedures for taking oil Oil Spill Science and Technology DOI: 10.1016/B978-1-85617-943-0.10005-X Copyright Ó 2011 Elsevier Inc All rights reserved 87 88 PART | III Oil Analysis and Remote Sensing samples, it is always important to ensure that the oil is not tainted from contact with other materials and that the sample bottles are precleaned with solvents, such as hexane, that are suitable for the oil.5 The simplest and most common form of analysis is to measure how much oil is in a water, soil, or sediment sample.6 Such analysis results in a value known as total petroleum hydrocarbons (TPH) The TPH measurement can be obtained in many ways, including extracting the soil, or evaporating a solvent such as hexane and measuring the weight of the residue that is presumed to be oil There now exist certified laboratories that use certified petroleum hydrocarbon measurement techniques.6 These should be used for all studies One of the most serious difficulties in older studies occurred when inexperienced staff tried to conduct chemical procedures Analytical methods are complex and cannot be conducted correctly without chemists familiar with the exact procedures Furthermore, field instrumentation requires calibration using standard procedures and field samples during the actual test These samples must be taken and handled by standard procedures Certified standards must be used throughout to ensure good Quality Assurance/Quality Control (QA/QC) procedures In this era, it is simply unacceptable not to use certified methods, laboratories, and chemists 5.2.1 Incorrect and Obsolete Methods Several attempts to perform oil analysis have been made using methods that are not scientifically valid One of these is the use of colorimetry This method has never been scientifically valid for oil measurement as oil does not have what is known as a color center, that is, a molecular absorption center for a specific band of light.7-9 As oil is a mixture of hundreds of compounds, there is obviously not a single light-absorbing centre This method results in oil measurements that are typically 100% incorrect Another series of methods involved extracting oil from soil or water using fluorinated or chlorinated hydrocarbons Since these extractants were ozonedepleting, they were removed from the market over 20 years ago The extracted hydrocarbons were then “measured” using infrared light, as hydrocarbons in such solvents absorb at specific wavelengths The method was the standard oil in soil technique in several countries and yielded repeatable results The ozone-depleting substances were replaced with hexane Hexane is not a good extractant of oil from soil, and thus these methods are not as popular as the older methods were The use of hexane also led to renaming the results of these methods from Total Petroleum Hydrocarbons (TPH) to hexaneextractables.10 There are several “meters” sold on the market that offer oil readings; however, none of these are reliable or accurate.8 Chapter | Introduction to Oil Chemical Analysis 89 Fluorometry is a technique sometimes used for measuring or estimating concentrations of oil in water A fluorometer uses UV or near UV to activate aromatic species in the oil.11 The UV activation energy is more sensitive to the naphthalenes and phenanthrenes, whereas the near UV is more sensitive to large species such as fluorenes The composition of the oil changes with respect to aromatic content as it weathers and is dispersed in water, with the concentration of aromatics increasing Thus, the apparent fluorescent quantity increases in this process It must be noted that fluorometers cannot truly be calibrated for the oil as there are many variables, as explained above The errors encountered all increase the apparent value of the oil concentration in the water column Incorrect calibration procedures can distort concentration values up to 10 times their actual value, or even more Correct analytical methods involve performing accurate gas chromatograph (GC) measurements both in the laboratory and in the field 5.3 CHROMATOGRAPHY The primary method for oil analysis, as well as for many chemicals in the environment, is gas chromatography; this method will be described in the subsequent section One should note that other chromatography methods and other analytical methods are sometimes used for oils These include liquid chromatography, sometimes used for PAH analysis and inductively coupled plasma (ICP) instruments for measuring metals in oils These and many other techniques are not described in this section 5.3.1 Introduction to Gas Chromatography The standard method for oil analysis is to use a GC.2,3,12,13,14 A small sample of the oil extract (typically measured in microliters, mL), often in hexane, and a carrier gas, usually helium or hydrogen, are passed through a capillary column The sample is injected into a heated chamber from where its vapors pass into the silica column The silica column is coated with absorbing materials, and, because the various components of the oil have varying rates of adhesion, the oil separates because these components are absorbed at different rates onto the column walls The gases then pass through a sensitive detector The injector, column, and detector are often maintained at constant temperatures to ensure repeatability The system is calibrated by passing known amounts of standard materials through the unit The amount of many individual components in the oil is thereby measured The components that pass through the detector can also be totaled, and a TPH value determined It is important to note that only the vapors pass into the column initially Heavier contaminants can foul the injector and first part of the column It is therefore important that the sample be subjected to a cleanup procedure before it is injected into the column Cleanup procedures can be complex and involve several steps 90 PART | III Oil Analysis and Remote Sensing While a GC measurement is highly accurate, this measurement does not include resins, asphaltenes, and some other components of the oil with higher molecular weight that not vaporize and pass through the column These heavier components can be determined separately using open column chromatography or precipitation techniques The detectors used in chromatography are important An important detector for petroleum hydrocarbons is the flame ionization detector (FID).2,3 The principle behind this instrument is simple as most compounds show variable ion conductivity burned in a hydrogen flame This detector is simple and has the advantage of yielding relatively similar signals for different hydrocarbons, thus making calibration and quantification simple Another detector commonly used for oils is the mass spectrometric detector The analytes from the GC column are introduced into a vacuum chamber and ionized, and then these ions are separated according to mass and passed to a detector The detected signals are then analyzed by a computer and output to the user as peaks of given mass or even possible compound identification The mass spectrometer provides information about the structure of the substance so that each peak in the chromatogram can be more positively identified The methods are abbreviated as GC-FID, if a gas chromatograph and flame ionization detector are used or GC-MS, if a gas chromatograph and a mass spectrometer detector are used A typical GC-FID chromatogram of a light crude oil with some of the more prominent components of the oil identified is shown in Figure 5.1.2,3 This chromatogram shows some of the many features of oil that are identified by this analytical technique The bulk of crude oils, especially light ones, have a large proportion of n-alkanes, as can be seen by the large peaks that constitute a large portion of this chromatogram This is a light crude oil that can be evidenced by the fact that the highest peak is C15 A more weathered crude might have its highest peak at C18 or more The top of the chromatogram is typically shaped as a curve, peaking to C15, as it is here Under the peaks is a hump, often called the unresolved complex mixture, or UCM This is an aggregate of largely unresolved peaks of alkane origin At C16, for example, there are already thousands of isomers that cannot be resolved by typical GC methods Between the n-alkane peaks are smaller peaks, most of which are aromatic compounds Two standard biomarkers (here, isoprenoids and branched alkanes) are usually evident in such a chromatogram, Pristane (near nC17) and Phytane (near nC18) These have been used to assess state of weathering; however, other compounds are now typically used Figure 5.2 shows the GC-FID chromatograms of 10 oils Figure 5.2A to C shows the chromatograms of three lighter crude oils: Arabian medium crude oil, Hedrun crude oil, and Gullfaks,2,3 Figure 5.2D shows a chromatogram of Orimulsion, a bitumen In this chromatogram one notes that almost all n-alkanes are not present, and the chromatogram largely consists of the 91 C28 C26 C24 C22 C20 Introduction to Oil Chemical Analysis C21 Chapter | Chromatographic retention time FIGURE 5.1 GC-FID of a light crude oil This chromatogram illustrates many features of the chromatograms of crude oils The bulk of crude oils, especially light ones, have a large proportion of n-alkanes, as can be seen by the large peaks that constitute a large portion of this chromatogram unresolved complex mixtures, or UCM Figure 5.2E shows the chromatogram of IFO-30, Intermediate fuel oil, which is a mixture of a diesel fraction and Bunker C Figure 5.2F shows the chromatogram of Bunker C, and Figures 5.2G-J show jet fuel, diesel fuel, lubrication oil, and number fuel oil, respectively The mass spectrometer provides information about the structure of the substance so that each peak in the chromatogram can be positively identified An important technique is that of SIM (selective ion monitoring), where one can monitor the ion most typically associated with the target compound This technique enables the detection and quantification of many compounds in oil that otherwise would not be separately resolved.2,3 Figure 5.3 shows three chromatograms first by GC-FID and then by GC-MS using SIM Figures 5.3A and B are chromatograms of a light Alberta crude oil; Figures 5.3C and D are chromatograms of California heavy crude oil, and Figures 5.3E and 5.3F are chromatograms of Orimulsion Bitumen The two chromatograms (e.g., FID/ SIM) are quite different The SIM chromatograms are no longer recognized as the types of oils as shown by FID However, one can see that the peaks are more clearly defined and that the SIM can provide different and important information The disadvantage of the SIM is that each peak must be quantified separately using an internal standard Most fuels and oils show a typical distribution pattern in GC-FID The idealized patterns can be seen in Figure 5.4, a figure that shows the alkane distribution All graphs are n-alkanes except for the lube oils where the alkanes are highly branched These bar graphs were created from 92 PART | III Oil Analysis and Remote Sensing FIGURE 5.2 GC-FIDs of several oils Figure 5.2A shows the chromatogram of Arabian medium crude oil Figure 5.2B is a chromatogram of Hedrun crude oil, a light oil Figure 5.2C is a chromatogram of Gullfaks, another light oil Figure 5.2D shows a chromatogram of Orimulsion, a bitumen In this chromatogram one notes that almost all n-alkanes are not present, and the chromatogram largely consists of the unresolved complex mixtures or UCM Figure 5.2E shows the chromatogram of IFO-39, Intermediate fuel oil, which is a mixture of a diesel fraction and Bunker C One can see the peaks of diesel fuel, peaking at about C14 and that of Bunker C, peaking at about C28 In Figure 5.2F the chromatogram of Bunker C is shown Figures 5.2G, 2H, 2I, and 2J show jet fuel B, diesel fuel, lubrication oil, and number fuel oil, respectively Chapter | Introduction to Oil Chemical Analysis 93 FIGURE 5.2 Continued quantitative analysis and approximate the alkane chromatograms of the same oils 5.3.2 Methodology Modern chromatographic methods require that the injected sample contents be of certain types and that they not foul the injector or column Thus, several cleanup methods have developed over the years.1,6 The basic methods involve extracting the oil using dichloromethane (DCM), sometimes in combination with other solvents such as hexane This procedure will leave the DCM insoluble material, such as soil and wood, and remove the DCM soluble material, which is largely petroleum oil Surrogate chemicals are often added at this stage; these substances are compounds, typically deuterated hydrocarbons, that are not present in oil and will serve to identify peaks in subsequent analyses The DCM extract is often filtered and treated to 94 PART | III Oil Analysis and Remote Sensing FIGURE 5.3 The GC-FID and GC-MS with SIM at ion 85m/e The left-hand columns are the GC-FID chromatograms, and the right-hand side are the GC-MS and SIM chromatograms Figures A and B are chromatograms of a light Alberta crude oil; Figures C and D are chromatograms of California heavy crude oil, and Figures E and F are chromatograms of Orimulsion Bitumen One notes that the two chromatograms (e.g., FID/SIM) are quite different The SIM chromatograms no longer have the recognizability of the types of oils as shown by FID However, one can see that the peaks are more clearly defined and that the SIM can provide separate information The disadvantage of the SIM is that each peak must be quantified separately using a standard Chapter | 95 Introduction to Oil Chemical Analysis Lube Oil Gasoline 10 12 14 Carbon Number 15 20 25 30 35 40 Carbon Number Jet Fuel Typical Crude 10 12 14 16 18 Carbon Number 10 15 Carbon Number 20 25 30 35 40 35 40 Diesel Fuel Bunker C 10 12 14 16 18 20 22 24 Carbon Number 10 15 20 25 30 Carbon Number FIGURE 5.4 The bar graph distribution of alkanes for typical oils and fuels These graphs were generated from the quantitative analysis of several oils It should be noted that the alkanes are typically n-alkanes for all oils except for lube oils, where they are highly branched alkanes remove water before injection into the GC At each point in this cleanup, the sample is quantified to allow measurement of those groups of materials removed These measurements then form the basis for various forms of TPH measurement One such method as developed by Dr Zhendi Wang of Environment Canada is shown in Figure 5.5.2,3 In the method illustrated in Figure 5.5, the sample is separated into aliphatic, aromatic, and polar fractions using an open silica column Several tests of this have been carried out to ensure that separation is complete Having these fractions separated ensures that subsequent chromatographic analysis is not affected by interferences between the three fractions The peaks that are typically quantified for analysis and possibly for identification are listed in Table 5.1.2,3 As described later, many of the these peaks are useful when combined in ratios Often these ratios are unique and can be used for positive identification of an oil There are many published methods and standards for oil analysis; several of these are listed in Table 5.2 96 PART | III Oil Analysis and Remote Sensing Weigh Sample add surrogates serially extract sample with dichloromethane/hexane filter and concentrate extract gravimetrically determine TPH silica column fractionation fraction aliphatics fraction fraction aromatics mixed 50% DCM/Hexane hexane gravimetric saturates aromatics determinations -Androstane d14-Terphenyl internal standards Hopane GC/MS SIM GC/MS (SIM) GC/FID PAHs n-alkane hopanes n-alkane quantification distribution & steranes half F1&F2 TPH 5- -Androstane fraction polars Methanol polars polars GC/FID Benzenes PAH alkylated homologues TPH FIGURE 5.5 Illustration of the Dr Wang analysis method developed for Environment Canada After cleanup procedures, the sample is separated into aliphatic, aromatic, and polar fractions This enables very clear chromatographic analysis without interference between these fractions This method yields many analytical parameters 5.4 IDENTIFICATION AND FORENSIC ANALYSIS The foregoing information can then be used to predict how long the oil has been in the environment and what percentage of it has evaporated or biodegraded.15-23 This is possible because some of the components in oils, particularly crude oils, are very resistant to biodegradation, whereas others are resistant to evaporation This difference in the distribution of components then allows the degree of weathering of the oil to be measured The same technique can be used to “fingerprint” an oil and positively identify its source Certain compounds are consistently distributed in oil, regardless of weathering, and these are used to identify the specific type of oil The effect of weathering is particularly important as it may negate the use of standard GC-FID to positively identify an oil.23, 28-31 Figure 5.6 shows the effect of weathering on the GC-FID chromatogram of a light crude oil As the oil weathers, more and more of the lower n-alkanes are lost to evaporation, the most important component of weathering Figure 5.6A shows the Chapter | 97 Introduction to Oil Chemical Analysis TABLE 5.1 Target Analytes/Compounds for Oil Spill Studies Analyte Analyte Target Ion Aliphatic Hydrocarbons BTEX and C3 Benzenes n-C8 Benzene 78 n-C9 Toluene 91 n-C10 Ethylbenzene 105 n-C11 Xylenes 105 n-C12 C2 - benzenes 105 n-C13 C3 - benzenes 105 n-C14 PAHs n-C15 Naphthalene 128 n-C16 C1 - naphthalene 142 n-C17 C2 - naphthalene 156 Pristane C3 - naphthalene 170 n-C18 C4 - naphthalene 184 Phytane Phenanthrene 178 n-C19 C1 - phenanthrene 192 n-C20 C2 - phenanthrene 206 n-C21 C3 - phenanthrene 220 n-C22 C4 - phenanthrene 234 n-C23 Fluorene 166 n-C24 C1 - fluorene 180 n-C25 C2 - fluorene 194 n-C26 C3 - fluorene 208 n-C27 Chrysene 228 n-C28 C1 - chrysene 242 n-C29 C2 - chrysene 256 n-C30 C3 - chrysene 270 n-C31 Biphenyl 154 (Continued ) 98 PART | III Oil Analysis and Remote Sensing TABLE 5.1 Target Analytes/Compounds for Oil Spill Studiesdcont’d Analyte Analyte Target Ion n-C32 Benzo[e]pyrene 252 n-C33 Benzo[a]pyrene 252 n-C34 Perylene 252 n-C35 Dibenzothiophene 184 n-C36 C1 - Dibenzothiophene 198 n-C37 C2 - Dibenzothiophene 212 n-C38 C3 - Dibenzothiophene 226 n-C39 n-C40 EPA Priority PAH pollutants Naphthalene 128 Phenanthrene 178 Fluorene 166 Chrysene 228 Acenaphthylene 152 Acenaphthene 153 Anthracene 178 Fluoranthene 202 Pyrene 202 Benz[a]anthracene 228 Benz[b]fluoranthene 252 Benzo[k]fluoranthene 252 Benzo(g,h,i)perylene 276 Biomarkers Triterpanes Tricyclic terpanes 191 Chapter | 99 Introduction to Oil Chemical Analysis TABLE 5.1 Target Analytes/Compounds for Oil Spill Studiesdcont’d Analyte Analyte Target Ion Tetracyclic terpanes 191 Pentacyclic terpanes 191 C23H42 191 C24H44 191 C27H46 (Ts) & (Tm) 191 C29H50&C30H52 ab-hopane 191 C30-35H52-62 22S/22R 191 Steranes C27 20 R/S-cholestanes 217,218 C28 20 R/S-ergostanes 217,218 C29 20 R/S-stigmastanes 217,218 unweathered oils with the Cn Benzenes and naphthalenes very obvious After about a 30% loss of oil through evaporation, the Cn Benzenes are lost, and many of the lower alkanes are shown in Figure 5.6B After 44.5% of the mass is evaporated, as shown in Figure 5.6C, even the naphthalenes are not clearly present It would be very difficult to simply compare weathered and unweathered oils simply by comparing the chromatograms Although there are some ways to partially compensate for this, modern technology uses other components of the oil to forensically identify oils 5.4.1 Biomarkers Biological markers or biomarkers are an important hydrocarbon group in petroleum analysis.32-34 Biomarkers are complex molecules derived from formerly living organisms Biomarkers found in crude oils, rocks, and sediments show little change in structures from their parent organic molecules, or so-called biogenic precursors (for example, hopanoids, and steroids), in living organisms Biomarker concentrations are relatively low in oil, often in the range of several hundred ppm Biomarkers are useful because they retain all or most of the original carbon skeleton of the original natural product; this structural similarity reveals more information about oil origins than other compounds Petroleum geochemists have historically used biomarker 100 TABLE 5.2 List of Standards Applicable to Oil Measurement Standards Organization Method Number ASTM Analyte Description Reference D5739-06 Standard Practice for Oil Spill Source Identification by Gas Chromatography and Positive Ion Electron Impact Low Resolution Mass Spectrometry GC-EI GC pattern Fingerprinting for oil identification 24 ASTM D3328-06 Standard Test Methods for Comparison of Waterborne Petroleum Oils by Gas Chromatography GC-EI GC pattern Fingerprinting for oil identification 24 ASTM D3415-98 Standard Practice for Identification of Waterborne Oils GC-FID oil ID Identification of oils on water 24 ASTM D3326-07 Standard Practice for Preparation of Samples for Identification of Waterborne Oils GC-FID oil ID Identification of oils on water 24 ASTM D5739-00 Standard Practice for Oil Spill Source Identification by Gas Chromatography and Positive Ion Electron Impact Low Resolution Mass Spectrometry GC-EI GC pattern Fingerprinting for oil identification 24 Oil Analysis and Remote Sensing Technique PART | III Title TABLE 5.2 List of Standards Applicable to Oil Measurementdcont’d Method Number ASTM Technique Analyte Description Reference F2059-06 Standard Test Method for Laboratory Oil Spill Dispersant Effectiveness Using the Swirling Flask GC-FID TPH TPH for water, chemical dispersion quantification 24 ASTM D5412-93 Standard Test Method for Quantification of Complex Polycyclic Aromatic Hydrocarbon Mixtures or Petroleum Oils in Water GC-EI PAHs Quantification of PAHS 24 ASTM D6352-04 Standard Test Method for Boiling Range Distribution of Petroleum Distillates in Boiling Range from 174 to 700 C by Gas Chromatography SIM-DIS Boiling Distribution Method to carry out a simulated distillation on oil e extended range 24 ASTM D2887-08 Standard Test Method for Boiling Range Distribution of Petroleum Fractions by Gas Chromatography SIM-DIS Boiling Distribution Method to carry out a simulated distillation on oil 24 ASTM D5307-97 Standard Test Method for Determination of Boiling Range Distribution of Crude Petroleum by Gas Chromatography SIM-DIS Boiling Distribution Method to carry out a simulated distillation on crude oil 24 ASTM D7169-05 Standard Test Method for Boiling Point Distribution of Samples with Residues Such as Crude Oils and Atmospheric SIM-DIS Boiling Distribution Method to carry out a simulated distillation 24 101 (Continued ) Introduction to Oil Chemical Analysis Title Chapter | Standards Organization 102 TABLE 5.2 List of Standards Applicable to Oil Measurementdcont’d Standards Organization Method Number Title Technique Analyte Reference Method to preserve oil samples 24 and Vacuum Residues by High Temperature Gas Chromatography D3325-90 Standard Practice for Preservation of Waterborne Oil Samples Sample Preservation API PHC Determination of Petroleum Hydrocarbons GC-FID PHC Petroleum Hydrocarbons 25 API GRO Determination of Petroleum Hydrocarbons GC-FID GRO Gasoline range organic compounds 25 API DRO Determination of Petroleum Hydrocarbons GC-FID DRO Diesel range organic compounds 25 EPA 846 Gas Chromatographic (GC) Methods GC-FID/EI organics General GC method 26 Oil Analysis and Remote Sensing ASTM PART | III Description TABLE 5.2 List of Standards Applicable to Oil Measurementdcont’d Method Number EPA Technique Analyte Description Reference 610 Determination of priority PAHS in municipal and industrial wastes GC-EI PAHs PAHs in wastes 26 EPA 1664 N-hexane Extractable Material (HEM; Oil and Grease) and Silica Gel Treated N-Hexane Extractable Material (SGT-HEM: Non-polar Material) by Extraction and Gravimetry gravimetry TPH N-hexane extractables in various substrates 26 CCME 1397 Canada-Wide Standard for Petroleum Hydrcarbons (PHC) in Soil GC-FID/EI TPH Suite of analysis techniques for hydrocarbons in soil 27 CCME 1399 Canada-Wide Standard for Petroleum Hydrcarbons (PHC) in Soil: Scientific Rationale GC-FID/EI TPH Background to suite of analysis techniques for hydrocarbons in soil 27 Reference Method for CanadaWide Standard for Petroleum Hydrcarbons (PHC) in Soil- Tier Method GC-FID/EI TPH Reference method to above for hydrocarbons in soil 27 CCME Introduction to Oil Chemical Analysis Title Chapter | Standards Organization 103 104 PART | III Oil Analysis and Remote Sensing FIGURE 5.6 Illustration of the effect of oil weathering on the chromatograms As the oil weathers, more and more of the lower n-alkanes are lost to evaporation, the most important component of weathering Figure A shows the unweathered oils with the Cn Benzenes and naphthalenes marked After about 30% loss of oil through evaporation, the Cn Benzenes are lost and also many of the lower alkanes as shown in Figure B After 44.5% of the mass is evaporated as shown in Figure C, even the naphthalenes are not clearly present It would be very difficult to compare weathered and unweathered oils simply by comparing the chromatograms fingerprinting in characterizing oils in terms of (1) the type(s) of precursor organic matter in the source rock (such as bacteria, algae, or higher plants); (2) correlation of oils with their source rocks; (3) determination of depositional Chapter | Introduction to Oil Chemical Analysis 105 environmental conditions (such as marine, terrestrial, deltaic, or hypersaline environments); (4) assessment of thermal maturity and thermal history of oil and the degree of oil biodegradation; and (5) providing information on the age of the source rock for petroleum For example, oleanane (C30H52) is a biomarker characteristic of angiosperms (flowering plants) found only in Tertiary and Cretaceous (