Aliphatic fractions

It is possible to indentify the ratios of carbohydrates (110-50 ppm), the ratio of aromatics (lignin) (150-130 ppm) and aliphatic acids and sterols (175 ppm, 40-15 ppm) from the spectra. In sample I cellulose signals were dominant, in sample II, on the other hand the aliphatic fractions were the major component. Sample III represented a balanced mixture of all three material groups. It was also possible to indentify the phosphate signal at 0 ppm by means of P-31 spectroscopy. 

As solvents, aromatic fractions are most useful with pentachlorophenol aliphatic fractions are effective as solvents for 2,4-D esters. 

Initially, the interest was on the oxidation of model substances or, in any case, of substances whose oxidation was already studied by other technologies, the results of which could be used for comparison. Phenol and oxalic acid were often considered to model the behaviour of the aromatic and aliphatic fractions of the waste, respectively. Single component artificial solutions were firstly considered. Then, attention was focused also to different substances, such as substituted phenols, or more complex molecules such as those of dyes. Moreover, an increasing number of papers dealt with the treatment of real wastes but in any case, at the moment, the study is performed on a laboratory scale or, in a few cases, on a pilot scale. Some studies reported the treatment of multi-component solutions which better simulate the real composition of the waste, at least concerning some peculiar characteristics of it. This is the case, e.g., of works on oxidation of dyes in which chlorides were added to the model solutions. 

Among the more oxidized compounds, oxalic acid has received significant attention (Martinez-Huitle et al. 2004, 2005 Ivandini et al. 2005) because often it constitutes the final product in the oxidative process of organics. It is generally selected as a model compound to represent the aliphatic fraction of organic substrate in the waste. 

Fig. 2. Gas chromatogram of hydrocarbons in the range Qj to C,6 (Studier et al., 1972). Only 6 of the 10 isomeric hydrocarbons with 16 C atoms are present in appreciable abundance 5 of them (underlined) are common to all three samples. The sample of the Precambrian Nonesuch shale (courtesy W. G. Meinschein) is a pure aliphatic fraction from which aromatic hydrocarbons had been removed by silica gel chromatography it will be discussed in Sec. 8.2. Abbreviations Me, methyl B.P., branched paraffin...

To simulate the abstraction of H by the tar, the aliphatic fraction in the tar is assumed to be retained together with some additional aliphatic material, which may be added directly or may contribute its hydrogen. When hydrogen from the aliphatic material is contributed, its associated carbons remain with the nonvolatile carbon fraction, which eventually forms the char [Figure 1(d)]. The nonvolatile carbon fraction is the aromatic carbon fraction minus the fraction of carbons released as CO from ether tight. 

The approach to evaluating the potential health effects for these transport fractions taken by ATSDR and the TPHCWG, however, uses a reduced number of fractions, namely three aliphatic fractions and three aromatic fractions. Health effects screening values based on representative chemicals or mixtures for each of the fractions were developed using ATSDR minimal risk levels (MRLs). 

The focus of this section is the selection, when possible, of appropriate MRLs for the assessment of health effects of the aromatic and aliphatic fractions of TPH. Approaches to cancer assessment are also discussed. The TPH fractions are environmental transport fractions, as suggested by the TPHCWG (1997c), with a slight modification to include all the BTEXs in a redefined aromatic EC5-EC9 fraction. 

Petrogenic hydrocarbons are characterized by a UCM of hydrocarbons in the aliphatic fraction, which is comprised primarily of branched and cyclic saturated hydrocarbons too numerous to be resolved by gas chromatographic techniques (21-23). Various... 

UV and fluorescence detectors can be used for SFC. Carbon dioxide and nitrous oxide have made possible the use of conventional GC flame detectors (24). Based on studies of aliphatic fraction of a solvent refined coal product with supercritical CO2 at 40 C and conventional FID detection, it was concluded... 

Figure 5. Capillary chromatograms of aa aliphatic fraction from a solvent refined coal liquid. Conditions (A) SFC...

In principle the aliphatic fraction can be cracked to aromatic hydrocarbons however, a major difficulty with any strategy of synthesising... 

This chapter presents data on the extent to which petroleum residues find their way into the sediments of the Bermuda platform. Bermuda was chosen since its mid-Atlantic location provides a range of sedimentary environments from shallow lagoonal to abyssal without the complications of contamination by continental shelf runoff and coastal pollution. We present results of the analyses of the aliphatic fraction of 50 surface sediments (from the upper 1-3 cm) and two species of benthic algae. 

The nature of the higher-molecular-weight aliphatic hydrocarbons from the Murchison has been controversial. Kvenvolden et al. [33] detected a wide variety of coeluting isomers dominated by polycyclic aliphatic structures. Oro et al. [41] reported Cg to Cj6 methyl and dimethyl alkanes, alkenes, and cycloalkanes. Studier et al. [42] detected straight-chain alkanes with some isoprenoidal hydrocarbons. It is now widely believed that straight-chain alkanes were the dominant components of the aliphatic fraction in the solar nebula. However, Cronin and Pizzarello [43] analyzed organic materials from the Murchison under less environmental contamination and concluded that the n-alkanes, methyl alkanes, and isoprenoid alkanes reported in the Murchison were terrestrial contaminants. These authors identified Ci5 to C3o cyclic alkanes as the major indigenous aliphatic components. 

Freeze-dried sediment was Soxhlet-extracted with dichloromethane. Concentrated extracts were fractionated by 107 chromatography on alumina/silica gel column. After elution of the aliphatic fraction with pentane, PCBs were eluted with 1 1 pentane-dichloromethane mixture. The fractions were then concentrated to 1 ml using Kuderna-Danish tubes heated in a water bath at 60°C... 

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