Aliphatic hydrocarbons, inland oil pollution incidents

A general classification of oil eg crude oil, petroleum, gas oil, is often satisfactorily achieved by gas chromatographic techniques possibly coupled with mass spectrometry or infrcired spectroscopy applied to a sample of the oil pollutant. The true identification invcuicibly requires samples from potential sources for comparison with the pollutant. 

Capillary colunms provide greater resolution and therefore more detail for comparison between a polluting oil and suspect sample. The enormous separation power available has been demonstrated in their application to petroleum analysis. Gouw [1] describes a versatile 10m x 0.25mm capillary column coated with CV-101, and its application to the separation of hydrocarbon mixtures in the C,-Ck n-alkane range. Columns of 152m x 0.25mm coated with 1-octadecene and operated at 30°C have been recommended for identification of crude oils [2]. 

A polar liquid phase was found more suitable for studying the major components of petrol, gas oil and diesel oil [3], forming true solutions in water. With such a phase, saturated hydrocarbons tended to elute before aromatic hydrocarbons, which were found to be the principal components in true solution, and therefore their investigation was facilitated, in the case of gas oil and diesel oil, forming true solutions in water. In the case of gas oil and diesel oil, no saturated hydrocarbons could be detected in solution. These authors reached the important conclusion that the determination of the origin of oil components in true aqueous solution could be more difficult because of selective solution of 

Invariably, dual packed columns have been employed, and one of the earliest articles devoted to the identification of petroleum products is that of Lively [4], who used dual 1.2m x 6mm columns packed with 20% SE-30 as the liquid phase and a Chromosorb solid support. Most subsequent workers in this field have employed the same or a similar liquid phase, usually at a lower loading of 4-5% and somewhat different column dimensions 1.2-3.6m x 3-6mm [5-9]. Chromosorb, or occasionally a similar solid support [7] was usually the solid support utilised after first being acid washed and treated with hexamethyl disilazine (HMDS) or dimethyl dichlorosilane (DMCS). Liquid phases of similar properties that have been employed are 5% and 10% OV-1, 20% SE-52,5% E301 [6], and 2.2% [10], 10% [13] and 20% [8] Apiezon L. These liquid phases are essentially non polar substances, but more polar phases, 5% and 10% polyethylene glycol 1500, have been used for investigations of the water-soluble components in diesel and gas oil and in petrol. 

In many publications, flame ionisation detectors and temperature programming were employed, the latter especially in the identification of less volatile oils. For routine investigations, isothermal conditions have been adopted in order to allow quicker analysis, but at the sacrifice of some fine detail in the chromatogram [8]. 

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