Mixtures unresolved complex

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. 

Fig. 12. Salient features of the GC-MS data for a hydrothermal petroleum (Guaymas Basin, Gulf of California, Mexico) (a) TIC trace of total oil, (b) mjz 191 key ion for hopanes, and ctmjz 217 key ion for steranes. Numbers refer to carbon chain (/ -alkanes) or skeleton, UCM = unresolved complex mixture, Pr = pristane, Ph = phytane, asterisks = other isoprenoids, ot, ot, R, S = configurations of biomarkers.

The characterization of a novel series of biomarkers is illustrated with the g 7 2-dialkylalkanes in bitumen from a hydrothermal system on the Mid-Atlantic Ridge. The total bitumen consists of hydrocarbons, a major UCM (unresolved complex mixture of branched and cyclic compounds) and mature biomarkers (e.g. hopanes) (Fig. 13a). The bitumen contains a series of cyclopentylalkanes Cfi 2n) that range from n = 14 to 34, with only even-chained pseudohomologs and a concentration maximum (Cmax) at n = 18. Their source is biogenic, based on the presence of only even-carbon number homologs, but the precursors are unknown. 

Figure 3. GC-FID chromatograms for thiophene compound fractions from Alberta petroleums. The peak labels are as follows 1. dibenzothiophene, 2. 4-methyldibenzothiophene, 3. 2- and 3-methyldibenzothiophene and 4. 1-methyldibenzothiophene. Samples are arranged in order of their depth of burial. Note the shift toward lower molecular weight compounds and a reduction in the amount of the unresolved complex mixture with increasing depth of burial. (Reproduced from Reference 34. Copyright 1989, American Chemical Society.)...

Unresolved complex mixture complexity of structural compounds found in petroleum hydrocarbons that cannot be fully resolved using current chromatographic... 

Figure 16 Bulk and molecular-level radiocarbon variations (expressed as %o, and age, yr BP) in surface (0-3 cm) sediment from the northeastern Bermuda Rise in the subtropical North Atlantic (33° 4TN, 57° 36 W, —4,500 m) planktonic foraminiferal calcite (diamonds), total OC (circles), C37-C39 alkenones (squares), fatty acids (down triangles), and hydrocarbons (up triangles). Carbon numbers of fatty acids and hydrocarbons are adjacent to the symbols (UCM = unresolved complex mixture of hydrocarbons). The sedimentation rate at this site during the Holocene averages 10-20 cmkyr (source Ohkouchi and Eglinton, unpublished).

Figure 3. Capillary GC-FID traces of saturated hydrocarbons in FL and HU fractions of sample LA. STD - co-injection standard, perdeuterated tetracosane IS - Internal standard, -terphenyl UCM - unresolved complex mixture. Chain lengths of odd-numbered n-alkanes are denoted.

Figure 3. Gas chromatograms of the aliphatic (fl) and aromatic (f2) fractions of the oil spill sample. The fl fraction contains identified n-alkanes in the range of n-C12 through n-C32 and pristane (pr) and phytane (py). UCM-unresolved complex mixture.

Localized contamination of water and sediment was observed near a docking area for commercial fishing boats, at Fisherman s Wharf along the Peace River. This pattern was unique to the area showing a bimodal unresolved complex mixture (UCM) and a total sediment hydrocarlaon content of 90 ug/1 (Site 10, Table I). 

Fig. 7. 8 Gas chromatogram of the total hydrocarbons fraction from a heavily biodegraded oil, showing the unresolved complex mixture (UCM).The elution range of the UCM is broadly equivalent to the re-alkane range shown in Fig. 4.16.The broken line shows the approximate zero signal (the elevated section towards right corresponds to the signal created by bleed of stationary phase at higher temperature see Box 4.3).

Measurements of bulk hydrocarbon groups including TPH, the unresolved complex mixtures (UCM), and the total saturates and total aromatics, contents of asphaltenes and resins,... 

FIGURE 27.24 GC-FID chromatograms of Fraction 3 for -alkane and TPH analysis of three unknown oil samples. These three samples show very similar GC chromatographic profiles and distribution patters, featured by dominance of unresolved complex mixture (UCM) of hydrocarbons with very small amount of resolved peaks. 

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