Infrared spectroscopy hydrocarbons

Most hydrocarbon resins are composed of a mixture of monomers and are rather difficult to hiUy characterize on a molecular level. The characteristics of resins are typically defined by physical properties such as softening point, color, molecular weight, melt viscosity, and solubiHty parameter. These properties predict performance characteristics and are essential in designing resins for specific appHcations. Actual characterization techniques used to define the broad molecular properties of hydrocarbon resins are Fourier transform infrared spectroscopy (ftir), nuclear magnetic resonance spectroscopy (nmr), and differential scanning calorimetry (dsc). 

Infrared Spectroscopy (ir). Infrared curves are used to identify the chemical functionality of waxes. Petroleum waxes with only hydrocarbon functionality show slight differences based on crystallinity, while vegetable and insect waxes contain hydrocarbons, carboxyflc acids, alcohols, and esters. The ir curves are typically used in combination with other analytical methods such as dsc or gc/gpc to characterize waxes. 

Methods utilizing characteristic physical properties have been developed for several chlorinated hydrocarbon insecticides. Daasch (18) has used infrared spectroscopy for the analysis of benzene hexachloride. By this means it is possible to determine the gamma-isomer content, as well as that of the other isomers of technical benzene hexachloride, provided the product is substantially free of the higher chlorinated cyclohexanes. 

Fiber optics have been used mainly to remotely sense chemical species via their intrinsic absorption or fluorescence. Methane and other hydrocarbons were a target analyte from the beginning. They can detected by infrared spectroscopy in the gas phase, as impressively shown by the... 

Topnir Not a chemical process but an instrumental process for on-line monitoring of hydrocarbon process streams by infrared spectroscopy. Developed by BP and offered for license in 1997. 

Infrared spectroscopy has been applied to the determination of particulate organic carbon in non-saline sediments, aliphatic hydrocarbons and total organic carbon in saline sediments and mixtures of organics in sludges. 

Concawe [8] have described a method for the determination of aliphatic hydrocarbons in soil based on carbon tetrachloride extraction followed by infrared spectroscopy or gas chromatography. 

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. 

Therefore, for infrared spectroscopic methods, the total petroleum hydrocarbons comprise any chemicals extracted by a solvent that are not removed by silica gel and can be detected by infrared spectroscopy at a specified wavelength. The primary advantage of the infrared-based methods is that they are simple and rapid. Detection limits (e.g., for EPA 418.1) are approximately 1 mg/L in water and 10 mg/kg in soil. However, the infrared method(s) often suffer from poor accuracy and precision, especially for heterogeneous soil samples. Also, the infrared methods give no information on the type of fuel present in the sample, and there is little, often no information about the presence or absence of toxic molecules, and no specific information about potential risk associated with the contamination. 

A number of procedures, based on microanalysis of samples for known physical properties (Chapter 8, 9, and 10), have also been employed. Eor example, field screening, which uses infrared spectroscopy, employing a portable version of the laboratory procedure has been used (Kasper et al., 1991). Eield turbido-metric methods favor the determination of high-boiling hydrocarbons and are... 

More sophisticated detection methods for gas chromatography are also employed in the analysis of hydrocarbons gas chromatography-mass spectrometry (EPA 8270C) and gas chromatography-Fourier transform infrared spectroscopy (EPA 8410). These procedures have a significant advantage in providing better characterization of the contaminants and thus are of particular use where some environmental modification of the hydrocarbons has taken place subsequent to soil deposition. 

Mille G, Guiliano M, Reymond H, et al. 1985. Analysis of hydrocarbons by Fourier transform infrared spectroscopy. Int J Environ Anal Chem 21(3) 239-260. 

Hudgins, D. M., and S. A. Sandford, Infrared Spectroscopy of Matrix Isolated Polycyclic Aromatic Hydrocarbons. 1. PAHs Containing Two to Four Rings, J. Phys. Chem. A, 102, 329-343 (1998a). 

Infrared and Raman spectroscopy. Stephens and Price (1970, 1972) used infrared spectroscopy to examine both ambient and laboratory-generated aerosols. They identified sulfate, nitrate, and ammonium ion absorption bands in ambient particles as well as bands indicating the presence of organics in diesel exhaust (C-H) and oxidized organics in irradiated hydrocarbon-NO, . mixtures. Since then, many studies using IR have been carried out and a variety of species identified, including COf , PO4-, and SiO A See Chapter 9.C.2 and Figs. 9.49, 9.50, and 9.51 for some typical FTIR spectra of atmospheric particles. 

Any alternate methods would have to have similar sensitivities, be relatively specific and able to analyze the samples quickly. We have found that infrared spectroscopy, when applied to hydrocarbon samples collected on charcoal tubes or vapor monitors, meets these requirements. 

The author wishes to thank the Hydrocarbon Research Group of the Institute of Petroleum for grants in aid of his work on infrared spectroscopy and hydrogen bondisig, and Dr. D. M. Simpson (Mrs. J. N. Agar) for critically reading the manuscript. 

Although the majority of the lipids in M. laidlawii membranes appear to be in a liquid-crystalline state, the system possesses the same physical properties that many other membranes possess. The ORD is that of a red-shifted a-helix high resolution NMR does not show obvious absorption by hydrocarbon protons, and infrared spectroscopy shows no ft structure. Like erythrocyte ghosts, treatment with pronase leaves an enzyme-resistant core containing about 20% of the protein of the intact membrane (56). This residual core retains the membrane lipid and appears membranous in the electron microscope (56). Like many others, M. laidlawii membranes are solubilized by detergents and can be reconstituted by removal of detergent. Apparently all of these properties can be consistent with a structure in which the lipids are predominantly in the bilayer conformation. The spectroscopic data are therefore insufficient to reject the concept of a phospholipid bilayer structure or to... 

Supercritical fluid extraction uses a supercritical fluid (Box 25-2) as the extraction solvent.20 C02 is the most common supercritical fluid because it is inexpensive and it eliminates the need for costly disposal of waste organic solvents. Addition of a second solvent such as methanol increases the solubility of polar analytes. Nonpolar substances, such as petroleum hydrocarbons, can be extracted with supercritical argon.21 The extraction process can be monitored by infrared spectroscopy because Ar has no infrared absorption. 

Separation and identification of this catenation compound was effected by chromatography and infrared spectroscopy, the latter being the reason why the hydrocarbon portion of ihe catenation compound was deuterated. 

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