Petroleum hydrocarbon analysis

There are two noncolumn cleanup methods, one of which uses acid partition (EPA SW-846 3650) to separate the base/neutral and acid components by adjusting pH. This method is often used before alumina column cleanup to remove acid components. The other method (EPA SW-846 3660) is used for sulfur removal and uses copper, mercury, and tetrabutylammonium sulfite as desulfurization compounds. Sulfur is a common interfering compound for petroleum hydrocarbon analysis, particularly for sediments. Sulfur-containing compounds are very common in crude oil and heavy fuel oil. Elemental sulfur is often present in anaerobically biodegraded fuels. Thus, abnormally high levels of sulfur may be... 

Furthermore, as a fuel evaporates or biodegrades, its pattern can change so radically that identification becomes difficult. Consequently, a gas chromatographic fingerprint is not a conclusive diagnostic tool. The methods used for total petroleum hydrocarbon analysis must stress calibration and quality control, whereas pattern recognition methods stress detail and comparability. 

To understand the relevance of infrared (IR) spectroscopy for total petroleum hydrocarbon analysis. 

The characterization of a spilled oil in a contaminated environmental sample can be important for the assessment of environmental damage, and also in the selection of appropriate response and cleanup measures. The identification of an oil spill source is also extremely important for settling any dispute relating to Hability and compensation. Petroleum hydrocarbon analysis may also be required to... 

Mineral Oil Hydraulic Fluids and Polyalphaolefin Hydraulic Fluids. Limited information about environmentally important physical and chemical properties is available for the mineral oil and water-in-oil emulsion hydraulic fluid products and components is presented in Tables 3-4, 3-5, and 3-7. Much of the available trade literature emphasizes properties desirable for the commercial end uses of the products as hydraulic fluids rather than the physical constants most useful in fate and transport analysis. Since the products are typically mixtures, the chief value of the trade literature is to identify specific chemical components, generally various petroleum hydrocarbons. Additional information on the properties of the various mineral oil formulations would make it easier to distinguish the toxicity and environmental effects and to trace the site contaminant s fate based on levels of distinguishing components. Improved information is especially needed on additives, some of which may be of more environmental and public health concern than the hydrocarbons that comprise the bulk of the mineral oil hydraulic fluids by weight. For the polyalphaolefin hydraulic fluids, basic physical and chemical properties related to assessing environmental fate and exposure risks are essentially unknown. Additional information for these types of hydraulic fluids is clearly needed. 

The third, and largely unexpected, case appeared as a problem in the analysis of petroleum hydrocarbons in seawater [24]. In this case, petroleum hydrocarbons, picked up presumably in the surface layers or surface film, were carried down by the sampling bottles and were measured as par t of the pollutant load of the deeper waters. While the possibility of absorption and subsequent release is obviously most acute with hydrophobic compounds and plastic samplers, it does raise a question as to whether any form of sampler which is open on its passage through the water column can be used for the collection of surface-active materials. The effects of such transfer of material maybe unimportant in the analysis of total organic carbon, but could be a major factor in the analysis of single compounds or classes of compounds. 

Commonly used methods for the determination of petroleum hydrocarbon contamination in soil are modifications of Environmental Protection Agency method 418.1, which use sonication or a Soxhlet apparatus for analyte extraction and either infrared spectrometry [5] or gas chromatography with flame ionization detection [6-7] for extract analysis. Regardless of the analytical method following the extraction, both modifications use Freon-113, which has been implicated as a cause of ozone depletion. Therefore, alternative methods are being sought for the determination of hydrocarbon contamination in environmental samples that reduce the need for this halogenated solvent. 

Petroleum pollution monitoring laboratories in the Mediterranean region participated (1984-1986) in two intercalibration exercises (MEDCALI and II) to evaluate the International Oceanographic Commission (IOC) Manual for petroleum hydrocarbon determination in sediment (IOC, Manuals and Guides, No. 11). The main source of error in the analysis was the extraction/ partition step. When the results were corrected for recoveries, relative standard deviations for w-alkancs, UCM (unresolved complex mixture) and total aromatics, which had previously been 60, 56 and 49%, respectively, were reduced to 17, 30 and 6%, respectively. 

California Department of Health Services, 1989, Total Petroleum Hydrocarbons (TPH) Analysis — Gasoline and Diesel In California Water Resources Control Board Leaking Underground Fuel Tank (LUFT) Manual, Appendix C. 

Kemblowski, M. W. andChiang, C. Y., 1988, Analysis of the Measured Free Product Thickness in Dynamic Aquifers In Proceedings of the National Water Well Association of Ground Water Scientists and Engineers and the American Petroleum Institute Conference on Petroleum Hydrocarbons and Organic Chemicals in Ground Water Prevention, Detection and Restoration, Vol. I, November, 1988, pp. 183-205. 

Wang, Y. Huang, Y. Huckins, J.N. Petty, J.D. 2004, Compound-specific carbon and hydrogen isotope analysis of sub-parts per bilUon level waterborne petroleum hydrocarbons. Environ. Sci. Technol. 38 3689-3697. 

In addition, the amount of total petroleum hydrocarbons is the measurable parameter of petroleum-based hydrocarbon in an enviromnental medium, whether it is air, water, or land. It is thus dependent on analysis of the medium in which it is found, and since it is a measured, gross quantity without identification of its constituents, the total petroleum hydrocarbons data still represent a mixture. Thus, the data derived from measmement of the petroleum hydrocarbons in a particular enviromnent is not a direct indicator of risk to humans or to the environment. 

Analysis for total petroleum hydrocarbons (EPA Method 418.1) provides a one-number value of the petroleum hydrocarbons in a given environmental medium. It does not, however, provide information on the composition (i.e., individual constituents) of the hydrocarbon mixture. The amount of hydrocarbon contaminants measured by this method depends on the ability of the solvent used to extract the hydrocarbon from the environmental media and the absorption of infrared light (infrared spectroscopy) by the hydrocarbons in the solvent extract. The method is not specific to hydrocarbons and does not always indicate petroleum contamination, since humic acid, a nonpetroleum material and a constituents of many soils, can be detected by this method. 

An important feature of the analytical methods for the total petroleum hydrocarbons is the use of an equivalent carbon number index (EC). This index represents equivalent boiling points for hydrocarbons and is the physical characteristic that is the basis for separating petroleum (and other) components in chemical analysis. 

Weisman, W. (Ed.). 1998. Analysis of Petroleum Hydrocarbons, Environmental Media Total Petroleum Hydrocarbon Criteria Working Group Series. Amherst Scientific Publishers, Amherst, MA. 

As already noted, the chemical composition of petroleum and petroleum products is complex and may change over time following release into the environment. These factors make it essential that the most appropriate analytical methods are selected from a comprehensive hst of methods and techniques that are used for the analysis of environmental samples (Dean, 1998 Miller, 2000 Budde, 2001 Sunahara et al., 2002 Nelson, 2003 Smith and Cresset, 2003). But once a method is selected, it may not be the ultimate answer to solving the problem of identification and, hence, behavior (Patnaik, 2004). There are a significant number of petroleum hydrocarbon-affected sites, and evaluation and remediation of these sites may be difficult because of the complexity of the issues (analytical, scientific, and regulatory not to mention economic) regarding water and soil affected. 

Once the sample preparation is complete, there are several approaches to the analysis of petroleum constituents in the water and soil (1) leachability or toxicity of the sample, (2) the amounts of total petroleum hydrocarbons in the sample, (3) petroleum group analysis, and (4) fractional analysis of the sample. These methods measure different petroleum constituents that might be present in petroleum-contaminated environmental media. 

Total petroleum hydrocarbon (TPH) (Chapter 4) analyses (Tables 7.1 and 7.2) are conducted to determine the total amount of hydrocarbon present in the environment. There are a wide variety of methods for measurement of the total petroleum hydrocarbon in a sample, but analytical inconsistencies must be recognized because of the definition of total petroleum hydrocarbons and the methods employed for analysis (Rhodes et al., 1994). Thus, in practice, the term total petroleum hydrocarbon is defined by the analytical method since different methods often give different results because they are designed to extract and measure slightly different subsets of petroleum hydrocarbons. 

The analysis for the total petroleum hydrocarbons (TPHs) in a sample as a means of evaluating petroleum-contaminated sites is also an analytical method in common use. The data are used to establish target cleanup levels for soil or water by regulatory agencies in the United States and in many other countries. 

The data obtained by the analysis have become key remediation criteria and it is essential that the environmental analyst (and others who may use the data) be knowledgeable about the various analytical methods. It is also important to know that minor method deviations may be found from region to region. For example, in terms of nomenclature, itself a complex and often ill-defined area of petroleum science (Chapter 1) (Speight, 1999), the analytical methods may refer to total petroleum hydrocarbons as mineral oil, hydrocarbon oil, extractable hydrocarbon, and oil and grease. 

There are many analytical techniques available that measure total petroleum hydrocarbon concentrations in the environment, but no single method is satisfactory for measurement of the entire range of petroleum-derived hydrocarbons. In addition, and because the techniques vary in the manner in which hydrocarbons are extracted and detected, each method may be applicable to the measurement of different subsets of the petroleum-derived hydrocarbons present in a sample. The four most commonly used total petroleum hydrocarbon analytical methods include (1) gas chromatography (GC), (2) infrared spectrometry (IR), (3) gravimetric analysis, and (4) immunoassay (Table 7.1) (Miller, 2000, and references cited therein). 

Methods based on gravimetric analysis (Table 7.2) are also simple and rapid, but they suffer from the same limitations as those of infrared spectrometric methods (Table 7.2). Gravimetric-based methods may be useful for oily sludge and wastewaters, which will present analytical difficulties for other, more sensitive methods. Immunoassay methods for the measurement of total petroleum hydrocarbon are also popular for field testing because they offer a simple, quick technique for in situ quantification of the total petroleum hydrocarbons. 

Immunoassay methods correlate total petroleum hydrocarbons with the response of antibodies to specific petroleum constituents. Many methods measure only aromatics that have an affinity for the antibody, benzene-toluene-ethylbenzene-xylene, and PAH analysis (EPA 4030, Petroleum Hydrocarbons by Immunoassay). 

Eor the analysis of petroleum hydrocarbons, a moderately polar material stationary phase works well. The plate is placed in a sealed chamber with a solvent (mobile phase). The solvent travels up the plate, carrying compounds present in the sample. The distance a compound travels is a function of the affinity of the compound to the stationary phase relative to the mobile phase. Compounds with chemical structure and polarity similar to those of the solvent travel well in the mobile phase. For example, the saturated hydrocarbons seen in diesel fuel travel readily up a plate in a hexane mobile phase. Polar compounds such as ketones or alcohols travel a smaller distance in hexane than do saturated hydrocarbons. 

Therefore, methods for the analysis of total petroleum hydrocarbon are frequently used to find areas of gross contamination but are often inadequate even for this task. Indeed, any one of several variables, such as differences in moisture content, can lead to analytical inconsistencies, and therefore the data do not consistently give reliable insights as to which part of the site is most contaminated. 

The purpose of this chapter is to describe well-established analytical methods that are available for detecting and/or measuring and/or monitoring total petroleum hydrocarbons and their metabolites, as well as other biomarkers of the exposure and effect of total petroleum hydrocarbons. The intent is not to provide an exhaustive list of analytical methods. Rather, the intention is to identify well-established methods that are used as the standard methods approved by federal agencies and organizations such as the Environmental Protection Agency and the National Institute for Occupational Safety and Health (NIOSH) or methods prescribed by state governments for water and soil analysis. Other methods... 

The method of analysis often used for the total petrolenm hydrocarbons (EPA 418.1) method provides a one-number valne of the total petroleum hydrocarbons in an environmental medium. It does not, by any stretch of the imagination, provide information on the composition (i.e., individual constituents of the hydrocarbon mixture). 

The conventional methods of analysis for total petroleum hydrocarbons (Chapter 7) have been used widely to investigate sites that may be contaminated with petroleum hydrocarbon products (see also EPA 418.1) for the determination of petroleum hydrocarbons. The important advantage of this method is that excellent sample reproducibility can be obtained, but the disadvantages are that... 

Currently, many regulatory agencies recommend the common methods (EPA 418.1, EPA 801.5 Modified) or similar methods for analysis dming remediation of contaminated sites. In reality, there is no standard for the measurement of total petroleum hydrocarbons since each method may need to be chosen or adapted on the basis of site specificity. 

It is not surprising that the data produced as total petroleum hydrocarbons (EPA 418.1) suffer from several shortcomings as an index of potential ground-water contamination or health risk. In fact, it does not actually measure the total petroleum hydrocarbons in the sample but rather, measures a specific range of hydrocarbon compounds. This is caused by limitations of the extraction process (solvents used and the concentration steps) and the reference standards used for instrumental analysis. The method specifically states that it does not accurately measure the lighter fractions of gasoline [benzene-toluene-ethylbenzene-xylenes fraction (BTEX)], which should include the benzene-toluene-ethylbenzene-xylenes fraction. Further, the method was originally a method for water samples that has been modified for solids, and it is subject to bias. 

When sampling in the enviromnent, it is often impossible to determine which chemical mixtures are causing a total petroleum hydrocarbons reading, which is one of the major weaknesses of the method. At minimum, before using contaminants data from diverse somces, efforts should be made to determine that field collection methods, detection limits, and quality control techniques were acceptable and comparable. This will help the analysts compare the analysis in the concentration range with the benchmark or regulatory criteria concentrations should be very precise and accmate. 

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