Residual Range Organics Testing

Petroleum is mainly composed of carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S) and other elements. Among them, carbon (C) and hydrogen (H) are the main elements, in which the content of carbon is 80% ~ 88% and the content of hydrogen is 10% ~ 14%. Fig.1 shows the petroleum fractions by carbon range, it can be seen that petroleum mainly include all kinds of fuel oil (gasoline, kerosene, diesel oil, etc.) and lubricating oil as well as liquefied petroleum gas, petroleum coke, paraffin wax, asphalt, etc. Petroleum contaminants are also split into different carbon ranges, and the typical carbon range of residual range organics (RRO) is C25 - C36, which mainly include bunker c, heavy fuel oils, lubricating oils, waxes and related products, asphalts and pitch. These oil and oil distillate spills can contaminate vast land areas, causing damages to the ecology and the economy of rural regions. Hence, in order to remediate hydrocarbon contamination, we desperately need to develop treatment and detect technology to control the content of these harmful compounds.

Fig.1. The petroleum fractions by carbon range

Alfa Chemistry is fully accredited at local and international level for the detection of petroleum contaminants, and we devote to be a world leader in laboratory analysis. We can provide a broad range of oil and oil byproducts testing at the same time ensure the accuracy of the measurement results in a relatively short period of time using advanced instruments.

The method of residual range organics (RRO) test

In general, residual range organics (RRO) are semi or non-volatile compounds, including aliphatic and aromatic hydrocarbons. Hence, there are two ways to test the content of residual range organics (RRO).

• 1. Gravimetric methods

This method mainly need to use the extraction technology, which separates compounds on the basis of their solubilities in two immiscible liquids. The compounds are normally separated from one liquid phase to another and the immiscible liquids usually consist of water and an organic solvent. For the test of residual range organics (RRO), the sample should be weighed firstly, and then solvent is added to extract oil. Secondly, the sample need to be heated till the solvent is evaporated completely, or pour the sample into a separatory funnel and the organic layer is removed. In the last, the sample will be weighed again. The content of residual range organics (RRO) can be obtained by calculating the quality of sample before and after.

• 2. Gas chromatography

Fig. 2. The gas chromatograph

Gas chromatography can be used to detect the residual range organics (RRO) because the different carbon ranges of the oil products have different volatilities (boiling points) [1]. Sample need to be extracted in solvent firstly, and then can be injected into GC with a carrier gas such as helium or nitrogen. The oil compounds will be separated over time depending on boiling point. Based on the area of the peak, we can calculate the content of the RRO with the pre-made standard curve.

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Reference

• M. Cecilia Medaura*; Eduardo C. ércoli. Bioconversion of petroleum hydrocarbons in soil using apple filter cake [J]. Brazilian Journal of Microbiology (2008) 39:427- 432.