Aliphatic hydrocarbons monitoring

Another variation of the preceding method is to apply HPLC to fractionate the cleaned-up aliphatic-aromatic fraction from flash colurim separation of soluble organic matter as it is performed in the Chevron laboratory, for example, as described in Reference 2. A Waters HPLC system equipped with a preparative Whatman Partisil 10 silica column (9.4 X 500 mm), a HPLC pump, and two detectors for separation monitoring (a UV and refractive index detector) are used, giving three fractions of aliphatic hydrocarbons, mono-, di-, and triaromatics and polar compounds. The hrst two fractions are eluted with hexane, whereas polar compounds are eluted with... 

The measurement technique was the crux of a paper by Acha et al.27 discussing the process of the dechlorination of aliphatic hydrocarbons. An ATR-FTIR sensor was developed to monitor parts per million (ppm) of trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride (CT) in the aqueous effluent of a fixed-bed dechlorinating bioreactor. It was found that the best extracting polymer was polyisobutylene (PIB) as a 5.8 pm film. This afforded detection limits of 2, 3, and 2.5 mg/1 for TCE, PCE, and CT, respectively. The construction and operation of the measurement system are detailed in the paper. 

A fiber-optic device has been described that can monitor chlorinated hydrocarbons in water (Gobel et al. 1994). The sensor is based on the diffusion of chlorinated hydrocarbons into a polymeric layer surrounding a silver halide optical fiber through which is passed broad-band mid-infrared radiation. The chlorinated compounds concentrated in the polymer absorb some of the radiation that escapes the liber (evanescent wave) this technique is a variant of attenuated total reflection (ATR) spectroscopy. A LOD for chloroform was stated to be 5 mg/L (5 ppm). This sensor does not have a high degree of selectivity for chloroform over other chlorinated aliphatic hydrocarbons, but appears to be useful for continuous monitoring purposes. 

The emission of a complete set of personal computers and monitors are described by Nakagawa et al. (2003). Several VOC like benzene, toluene, etc. were identified and quantified. The results are shown in Table 17.3. The emission rates of aliphatic hydrocarbons, terpenes, esters, ketones, alcohols and halogens were not found to be significantly different for PCs with CRT and TFT monitors. In the case of aromatic hydrocarbons the emission rates were higher if a PC with CRT monitor was used. The same was found for aldehyde emissions but the differences in emission rates were lower. The separate test CRT monitor and the associated computer in this study proved that the monitor was the main source of chemical emissions. 

The application of GC-MS to PAH-analysis will allow considerable simplification of the work-up procedure. As far as solubility and dynamic range considerations will permit, the major PAH in airborne particulate matter samples can be accurately measured in the electron impact single or multiple ion monitoring mode, using the molecular ions of the respective PAH as specific ions, in the presence of much larger amounts of aliphatic hydrocarbons and carboxylic acids. Polar and ionic material is first removed from the combined benzene-methanol extract by liquid-liquid partition in water-diethylether. After drying, the addition of diazomethane results in derivatisation of the acidic components and the sample can be injected onto the column (Van Vaeck and Van Cauwenberghe (30)). 

The monomer conversion and reduced viscosity were monitored by continuously inverting and diluting the emulsion phase using a small reactor sample stream and a breaker surfactant solution, followed by UV absorption and viscometric detection. Sorbitan monooleate (Span 80) was used as the emulsifier, Exxsol D80 was the oil phase (aliphatic hydrocarbon), and Surfonic N-95 (alkylphenol ethoxylate), a nonionic surfactant, was chosen to make the phase inversion. 

Real-time continuous monitoring of VOCs at a site near the Houston Ship Channel during the Texas Air Quality Study 2(X)0 was reported by Karl et al. [118]. The anthropogenic VOCs that were observed included aromatic compounds (e.g. benzene, toluene and xylenes), aliphatic hydrocarbons (e.g. propene and isoprene), oxygenated VOCs... 

The primary products from autoxidation are hydroperoxides, which are often simply referred to as peroxides. Peroxides are odorless and colorless, but are labile species that can undergo both enzymatic and nonenzymatic degradation to produce a complex array of secondary products such as aliphatic aldehydes, alcohols, ketones, and hydrocarbons. Many of these secondary oxidation products are odiferous and impart detrimental sensory attributes to the food product in question. Being able to monitor and semi-quantitate the development of peroxides by objective means (e.g., PV determination) over time is important for food scientists who want to characterize the quality of an oil or a lipid-containing food product, even though the peroxides themselves are not directly related to the actual sensory quality of the product tested. 

The separation shown in figure 7 of a mixture of aliphatic and aromatic hydrocarbons was monitored using both a katherometer detector that responded to all solutes and the emissivity detector that selectively responded to the aromatics. It is seen that the emissivity... 

A device based on a crystal coated with nugol-transchloro-carbonyl bis.(triphenylphosphine)irridium(l) was reported to detect aromatic hydrocarbons preferentially over aliphatic ones and ordinary olefines (30). Xylenes, benzaldehyde, 1,3,5-trimethylben-zene, anisole, n-butyl benzene, could be detected at low concentrations, but hexane, heptane, octane, and cyclohexane were detected at high concentrations. The coating was less sensitive to benzene and toluene, and did not respond to moisture. The detector was used to monitor auto exhaust for aromatic hydrocarbons. 

Hydrocarbon, typically an alkyl chain of 12-16 carbons, constitutes the major of surfactant molecules, offering H and nuclei for NMR studies. Being /=l/2 nuclei, their relaxation is due mainly to dipole-dipole interactions. The easy access and the relatively high sensitivity (particularly important in early continuous-wave NMR studies) has made H NMR (in particular bandwidth measurements) studies particular popular. Micellar growth can easily be studied in a qualitative manner by monitoring the bandwidths of aliphatic (-CH2-) protons in the spectrum. A quantitative analysis is, however, complicated by the coupling of the various protons, with locally different motional characteristics, along the alkyl chain. 

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