Saturated hydrocarbons, chromatograms

Figure 4. Chromatograms for saturated hydrocarbon fractions showing predominance of n-paraffins (sequence from...

More accurate quantitative analyses can be carried out by GC or LC. A suitable internal standard is usually required it must be chemically stable and involatile under the conditions of the experiment (prior to injection into the chromatography apparatus), and must be resolved from the other signals in the chromatogram. It is usually added to the product mixture after the reaction has been completed but before any extraction, purification or analysis steps are undertaken. Saturated hydrocarbons of Cio or above are typically used as internal standards for GC [7]. Response factors are obtained for each component of... 

Figures 3a—d. Capillary column gas chromatograms of the saturated hydrocarbon fractions of selected samples from the laminite series of the Nordlinger Ries. n-Alkanes are indicated by number of carbon atoms phy = phytane, G = gammacerane, G = gammacerane-2-ene, I.S. = internal standard (squalane).

Figure 3. Mass chromatogram of m/z 218 of the saturated hydrocarbon fraction of the Rozel Point oil. 5a(H),14a(H),17a(H)- and 5a(H),140(H),170(H)-steranesare differentiated as shown.

Quantitation. Pristane and phytane concentrations (/xmol/kg bitumen) were obtained by integration of their peak areas and that of the deuterated C22 anteisoalkane (I, Table II) standard in the FID chromatograms. The concentration of the other compounds in the saturated hydrocarbon fraction were obtained by integration of appropriate peaks in mass chromatograms of m/z 57 (n-alkanes, standard), m/z 367 (extended hop-17(21)-enes), m/z 191 (hopanes), m/z 217 (steranes). Because of differences in yield of these ions for different classes of compounds the values for hop-17(21)-enes, steranes and hopanes are approximate. 

Gas chromatograms of three saturated hydrocarbon fractions, roughly representing the different facies (Figure 2), show that some relative and absolute variations exist between the three facies. n-Alkanes, pristane, phytane and the extended hop-17(21)-enes are indicated. The most prominent changes within different compound classes in the saturated hydrocarbon fraction are highlighted below. 

Figure 2. Gas chromatograms (CP Sil-5) of the saturated hydrocarbon fractions of the indicated samples from Facies A, B and C of the Jurf ed Darawish oil shale.

This resemblance is highly significant if one considers that 10,359 structural isomers exist for saturated hydrocarbons with 16 C atoms (Lederberg, 1972). Apparently the meteoritic hydrocarbons were made by FTT reactions, or some other process of the same extraordinary selectivity. The Miller-Urey reaction, incidentally, shows no such selectivity. Gas chromatograms of hydrocarbons made by electric discharges in methane show no structure whatsoever in the region around Cjg (Ponnamperuma et al., 1969). Apparently all 10 possible isomers are made in comparable yield, as expected for random recombination of free radicals. 

Figure 4 GC-FID chromatograms of the saturated hydrocarbon fraction of sediments collected from sampling Area A. Numbers indicate n-alkane carbon number represented by the adjacent chromatographic peak. I.S. indicates the position of the internal standard (5,Ct-androstane) chromatographic peak.

Trace Organics. High resolution gas chromatograms from analyses of the saturated hydrocarbon fractions of four sediment samples collected from the lake In January 1983 are shown In Figure 4. 

Figure 17. Chromatograms of saturated hydrocarbons at 200°C on the following adsorbents (I) X, (II) Xh-r,(III) Xh-a- PeaJcs (1) n-pentane, (2) n-hexane, (3) n-heptane, (4) n-octane,(5) n-nonane. Chromatographic conditions glass column (0,4 mx2,5 mm i.d.), carrier gas - hydrogen, flow rate 32 cm /min. Thermal conductivity detector, sample size 1 //I.

Figure 3. Glass capillary gas chromatogram (high resolution) of saturated hydrocarbons from Stomach contents of cod near the Argo Merchant oil slick, which is virtually identical to saturated hydrocarbons in Argo Merchant cargo oil. Numerals denote n-alkane chain length (55).

The GC-FID analysis is conducted by injection of 1 to 2 fil of FI or F3 into a gas chromatograph equipped with a high resolution capillary column (operated in sphtless injection mode). The injector and detector temperatures are set at 290 and 300°C, respectively. The GC temperature program is selected to achieve near-baseline separation of all of the saturated hydrocarbons. Quantitation of the individual components is performed by the internal standard method. The relative response factor (RRF) for each component is calculated relative to the internal standard. The TPH is also quantified by the internal standard method using the baseline corrected total area of the chromatogram and the average hydrocarbon response factor determined over the entire analytical range. ... 

FIGURE 23. Gas chromatograms of (a) a whole crude oil from the Altamont Bluebell Field, Unita Basin, and (b) saturated hydrocarbons from a Canadian Arctic Island sedimentary rock, GC on eutectic column ... 

FIGURE 24. Gas chromatogram of branched and cyclic saturated hydrocarbons from the Green River oil shale. Same column as in Figure... 

The chromatograms of the liquid phase show the presence of smaller and larger hydrocarbons than the parent one. Nevertheless, the main products are n-alkanes and 1-alkenes with a carbon number between 3 to 9 and an equimolar distribution is obtained. The product distribution can be explained by the F-S-S mechanism. Between the peaks of these hydrocarbons, it is possible to observe numerous smaller peaks. They have been identified by mass spectrometry as X-alkenes, dienes and also cyclic compounds (saturated, partially saturated and aromatic). These secondary products start to appear at 400 °C. Of course, their quantities increase at 425 °C. As these hydrocarbons are not seen for the lower temperature, it is possible to imagine that they are secondary reaction products. The analysis of the gaseous phase shows the presence of hydrogen, light alkanes and 1-alkenes. 

Heavy hydrocarbons were obtained by solvent extraction (4) of sediments, deasphalting with pentane, and separation by liquid chromatography (5) into saturate, aromatic, NSO-eluted, and asphaltene fractions. Saturate fractions were analyzed by gas-liquid chromatography (6) on these chromatograms (Figures 4 and 6) n-paraffins stand up as peaks above the naphthenic background. 

It is well known for example in the saturated LDPE polymer chains that a certain number of double bounds exist which can be measured with IR spectroscopy. By extraction with non-polar solvents and GC separation, numerous alkanes and alkenes can be identified which are dissolved in small concentrations in the PE. The odor thresholds of these compounds are in general so high that these hydrocarbons play no sensory role. As a result no correlation can be made between the total amount of volatile compounds isolated from PE or the fingerprint chromatogram from a GC separation and the sensory properties of a sample. The relevant sensory compounds as a rule are the (order of magnitude) less concentrated oxygenated compounds in the... 

The gas chromatograms of the hydrocarbon fractions indicate that asphaltene consists of complex macromolecules that decompose to yield a wide distribution (from C10 to - Qjs) of molecules within each of the saturate, mono-, di-, and poly aromatic and polar classes. 

Petroleum hydrocarbon identification was based primarily on the GC-FID chromatogram patterns of the saturated and unsaturated... 

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