Infrared spectroscopy aromatic hydrocarbons

Principal component analysis has been used in combination with spectroscopy in other types of multicomponent analyses. For example, compatible and incompatible blends of polyphenzlene oxides and polystyrene were distinguished using Fourier-transform-infrared spectra (59). Raman spectra of sulfuric acid/water mixtures were used in conjunction with principal component analysis to identify different ions, compositions, and hydrates (60). The identity and number of species present in binary and tertiary mixtures of polycycHc aromatic hydrocarbons were deterrnined using fluorescence spectra (61). 

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). 

The acid, base, and neutral Lewis base fractions consist of polar molecules capable of hydrogen bonding and, therefore, of intermolecular association. These polar fractions, which constitute nearly two-thirds of the 675°C+ residuum, have high concentrations of heteroelements in comparison to the nonpolar aromatic and saturate hydrocarbons, as shown in Table IX for the residuum from a Russian crude oil. Infrared spectroscopy of the acid fraction revealed mostly pyrroles with phenols but only traces of... 

Other applications of subcritical water extraction-solid-phase microextraction are the determination of terbuthylazine and its metabolites [123], polycyclic aromatic hydrocarbons [124,125] and polychlorobiphenyls [63]. Yang and Her [193] collected 1-chloronaphthylene, nitrobenzene and 2-chloro-toluene in soil on a hydrophobic polyisobutylene disc prior to analysis by attenuated total reflectance Fourier transform infrared spectroscopy. 

With the demonstration of supercritical fluid extraction, an obvious extension would be to extract or dissolve the compounds of interest into the supercritical fluid before analysis with SFC.(6) This would be analogous to the case in HPLC, where the mobile phase solvent is commonly used for dissolving the sample. The work described here will employ a system capable of extracting materials with a supercritical fluid and introducing a known volume of this extract onto the column for analysis via SFC. Detection of the separated materials will be by on-line UV spectroscopy and infrared spectrometry. The optimized SFE/SFC system has been used to study selected nonvolatile coal-derived products. The work reported here involved the aliphatic and aromatic hydrocarbon fractions from this residuum material. Residua at several times were taken from the reactor and examined which provided some insight into the effects of catalyst decay on the products produced in a pilot plant operation. 

The non-saponifiable part can be further investigated by means of infrared spectroscopy or UV fluorescence. This can give indications as to which types of hydrocarbons are present (paraffins or aromatic substances or mixtures of both). 

The composition of coke (H/C ratio) is analyzed by measuring the amount of CO2 produced and the O2 consumed during a TPO analysis (107). Typical values of this ratio range between 0.5 and 0.8 (107). It has been found that the ratio increases as the amount of metal increases. Infrared spectroscopy showed that coke is formed mainly by aromatics (83,108). The extraction with solvents only removes a small fraction of the total amount of coke. This soluble fraction mainly contains polyaromatic hydrocarbons. As reaction time increases, the number of... 

Infrared spectroscopy is an excellent technique for determining the structure of a polymer. For example, polyethylene and polypropylene have relatively simple spectra because they are saturated hydrocarbons. Polyesters have stretching frequencies associated with the C=0 and C—O groups in the polymer chain. Polyamides (nylon) show absorptions that are characteristic for the C=0 stretch and N—H stretch. Polystyrene has characteristic features of a monosubstituted aromatic compound (see Technique 25, Figure 25.12). You may determine the infrared spectra of the linear polyester from Experiment 46A and polystyrene from Experiment 46C in this part of the experiment. Your instructor may ask you to analyze a sample that you bring to the laboratory or one supplied to you. 

None of the unknowns to be issued for this experiment will be simple aromatic hydrocarbons. All aromatic compounds will have a principal functional group as a part of their structure. Nevertheless, in many cases it will be useful to be able to recognize the presence of an aromatic ring. Although infrared and nuclear magnetic spectroscopy provide the most reliable methods of determining aromatic compounds, often they can be detected by a simple ignition test. 

Oomens J, Tielens AGGM, Sartakov BG, Von Helden G, Meijer G (2003) Laboratory infrared spectroscopy of cationic polycyclic aromatic hydrocarbon molecules. Astrophys J 91 968-985... 

Figure 4 IR chromatogram of the first 40 min of a GC-IR separation of aromatic components in a sample of gasoline. The peaks represertt the total integrated absorbance intensity in the region 900-600 cm Reprinted with permission from Diehl JW, Finkbeiner JWand DiSanzo FP (1995) Determination of aromatic hydrocarbons in gasolines by gas chromatography/Fourier transform infrared spectroscopy. Analytical Chemistry 7 2015-2019. Copyright 1995 American Chemical Society.

An alternative method for fractionating and purifying petroleum hydrocarbons prior to GC or HPLC separation has been developed (Theobald 1988). The method uses small, prepacked, silica or Cjg columns that offer the advantage of rapid separation (approximately 15 minutes for a run) good recovery of hydrocarbons (85% for the Cjg column and 92% for the silica column) reusability of the columns and for the silica column in particular, good separation of hydrocarbon from non-hydrocarbon matrices as may occur with environmental samples. Infrared analysis and ultraviolet spectroscopy were used to analyze the aromatic content in diesel fuels these methods are relatively inexpensive and faster than other available methods, such as mass spectrometry, supercritical fluid chromotography, and nuclear magnetic resonance (Bailey and Kohl 1991). 

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