Analysis of hydrocarbons

Various analytical techniques used for hydrocarbon analyses of sea water samples, ultraviolet and fluorescence spectrophotometry (Keizer and Gordon, 1973), infrared spectrometry (Carlberg and Skarstedt, 1972), liquid column chromatography together with the determination of heat of adsorption (Zsolnay, 1977b) provide only data about a fraction of the hydrocarbons or yield a value equivalent to the total hydrocarbon concentration. Thus, we will only consider studies where hydrocarbons are precisely determined by gas—liquid chromatography and mass spectrometry. 

The preliminary extraction of hydrocarbons and other compounds from sea water or sediment is followed by the isolation of hydrocarbons from the extract. At this stage a variety of analytical methods may be applied to analyse for total hydrocarbons or selected fractions. 

Isolation of the hydrocarbons from other lipids The total lipid extract may be subjected to removal of elemental sulphur by passage through an activated copper column (Blumer, 1957) and then to chromatographic separation on adsorbent columns or thin layer plates. For column chromatography, silic el is used with a short alumina bed on the top of the silic el. Both adsorbents should be partially deactivated by the addition of water (2—5%) to prevent the formation of artifacts (Blumer, 1970). Elution with a non-polar solvent such as hexane or pentane and subsequently with mixtures of non-polar and polar solvents, e.g. benzene and methanol, permits the isolation of several fractions containing saturated, unsaturated, aromatic hydrocarbons and more polar compounds (methyl esters, alcohols, acids, phenols and heterocyclic compounds). The interference from esters encountered in the isolation of aromatic hydrocarbons can be avoided prior to separation by saponification of the esters of fatty acids, which are easily removed. 

Preparative chromatography on thin layers of silica in the pentane-ethyl 

Other separating techniques may be used to separate total hydrocarbons into different classes. Thus, the normal paraffins are selectively removed by 5 A molecular sieve (Mortimer and Luke, 1967) or by urea adduction, although it is less specific than the former method. Unsaturated hydrocarbons are separated from the saturated fraction by thin layer or column chromatography on silicic acid/AgNOj. 

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Analysis of Hydrocarbons Contained in a Gasoline by Gas Phase Chromatography... 

CASE STUDY 1 INCIDENT ANALYSIS OF HYDROCARBON LEAK FROM PIPE... 

H. Tani and M. Furuno, Rapid analysis of hydrocarbons and inert gases hy a multidimensional gas cltromatograph , J. High Resolut. Chromatogr. Chromatogr. Commun. 9 712-716(1985). 

Repeat the analysis of hydrocarbon cracking in Example 5.6 with... 

Repeat the analysis of hydrocarbon cracking in Example 5.6 for the case where there is external heat exchange. Suppose the reaction is conducted in tubes that have an i.d. of 0.012 m and are 3 m long. The inside heat... 

Wasik SP, Brown RL (1973) Determination of hydrocarbon solubility in seawater and the analysis of hydrocarbons in water-extracts. In Proceedings of the conference on prevention and control of oil spills. American Petroleum Institute, Washington, DC, pp 223-237... 

Blaylock JW, Bean RM, Wildung RE (1974) Determination of extractable organic material and analysis of hydrocarbon types in lake and coastal sediments. Special publication no. 409. National Bureau of Standards, Washington, DC, p 217... 

As an analyst you understand the meaning of the scientific data you produce. However, it must be remembered that laymen often do not and so the data need to be documented in a form that is easily understood. For example, the chromatographic analysis of hydrocarbon oil from an oil spill can produce a chromatogram with over 300 components. Explaining the significance of such data to a jury will be of little benefit. However, overlaying it with a standard trace can demonstrate pictorially whether there is a similarity or not. The customer requires information from the analyst to prove a point. If the data are not fully documented, then the point cannot be proven. A customer who has confidence in a laboratory will always return. 

Evaluation of Methods for the Determination of Fluoride in Water Samples. 2 Analysis of a Competitive Product. 3 The Assessment of the Heavy Metal Pollution in a River Estuary. 4 The Analysis of Hydrocarbon Products in a Catalytic Reforming Study. 

The Analysis of Hydrocarbon Products in a Catalytic Reforming Study Example 12.2.4... 

Detection of irradiated food containing fat - Gas chromatographic analysis of hydrocarbons... 

Abstracts - International Symposium on the Analysis of Hydrocarbons and Halogenated Hydrocarbons" sponsored by Canada Center for Inland Waters, and University of Toronto, May, 1978. 

More sophisticated detection methods for gas chromatography are also employed in the analysis of hydrocarbons gas chromatography-mass spectrometry (EPA 8270C) and gas chromatography-Fourier transform infrared spectroscopy (EPA 8410). These procedures have a significant advantage in providing better characterization of the contaminants and thus are of particular use where some environmental modification of the hydrocarbons has taken place subsequent to soil deposition. 

Heine, C.E. Geddes, M.M. Field-Dependent [M-2H] Formation in the Field Desorption Mass Spectrometric Analysis of Hydrocarbon Samples. Org. Mass Spectrom. 1994,29, 277-284. 

Mille G, Guiliano M, Reymond H, et al. 1985. Analysis of hydrocarbons by Fourier transform infrared spectroscopy. Int J Environ Anal Chem 21(3) 239-260. 

We believe it has been shown that this method for infrared analysis of hydrocarbons collected on charcoal tubes and vapor monitors is a valid and acceptable one. Further work is being done to validate the method for other hydrocarbons such as petroleum naphtha, Stoddard solvent, and other JP aviation fuels. Additionally, work is being done to determine the 3M monitor sampling rate for JP-4. 

Industrial analysis of hydrocarbon gases 25 years ago was limited almost to Orsat-type absorptions and combustion, resulting in crude approximations and inadequate qualitative information. The more precise method of Shepherd (56) was available but too tedious for frequent use. A great aid to the commercial development of hydrocarbon gas processes of separation and synthesis was the development and commercialization of high efficiency analytical gas distillation units by Podbielniak (50). In these the gaseous sample is liquefied by refrigeration, distilled through an efficient vertical packed column, the distillation fractions collected as gas and determined manometrically at constant volume. The operation was performed initially in manually operated units, more recently in substantially automatic assemblies. 

Although infrared absorption analysis of hydrocarbon mixtures was described by Lecomt and Lambert (34), the extensive application of this technique to the examination of petroleum products awaited the commercial availability of a practical instrumental unit and adequately described methods such as those of Brattain and Beeck (11) for a two component mixture and Brattain et al. (12) for a multicomponent mixture of hydrocarbon gases. By such methods the possible qualitative constituents of the sample must, of course, be known and their number limited to a maximum probably simultaneously present. 

Figure 2.16—A miniature chromatograph. Instrument using a capillary column and a photoionisation detector. The instrument, weighing 4 kg including the carrier gas (C02), is mainly used for the analysis of volatile organic compounds (VOCs) in air pollution. The photoionisation detector, which is of limited use because of its variable sensitivity, is well suited for the analysis of hydrocarbons. The high powered UV source emits photons that have energies between 10 and 11 eV, ionising the compounds that exit the column, with the exception of the carrier gas. The ionic current generated is amplified using an electrometer and is proportional to the concentration of analytes (reproduced by permission of Photovac).

Spectrographic data are gradually becoming more important for the analysis of hydrocarbon mixtures. These methods will not be discussed as they fall outside the scope of this monograph. 

Fig. 80. Ring analysis of hydrocarbons obtained from polymerized fatty acid esters.

The use of physical constants is, however, limited in the case of more complicated chemical processes the more complex the chemical change, the larger the number of physical properties necessary to investigate completely the chemical transformations. This especially holds when catalysts are involved in the reactions. When studying catalytic reactions we are dealing with catalysts as mixtures of a far more complicated nature than is the case, for example, in the structural analysis of hydrocarbon mixtures. The latter can be described, as was shown in the preceding sections, by means of a limited number of physical constants, from which either the chemical composition of the mixture or a series of other physical constants can easily be derived. For the characterization of catalysts completely different principles have to be applied even in simple cases, because in the case of a catalyst it is not chiefly its chemical composition that is important, but its chemical activity, which determines the result obtained by its chemical action. 

M. G. Block, R. B. Callen and J. H. Stockinger, The analysis of hydrocarbon products obtained from methanol conversion to gasoline using open tubular GC columns and selective olefin absorption , J. Chromatogr. Sci. 15 504-512 (1977). 

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