Extractable Petroleum Hydrocarbons Testing

Petroleum is also called petroleum hydrocarbon, of which the components mainly include chain alkanes, cycloalkanes, aromatic hydrocarbons, olefins, and a few hydrocarbon derivatives. Among them, hydrocarbons accounts for 95% ~ 99% in the petroleum composition [1].Extractable petroleum hydrocarbons (EPH) can be divided into extractable aliphatic hydrocarbons and extractable aromatic hydrocarbons by specified carbon-number-ranges. Extractable aliphatic hydrocarbons are collectively quantitated within two ranges: C9 through C18 and C19 through C36. Extractable aromatic hydrocarbons are collectively quantitated within the C11 through C22 range. Many of these hydrocarbons have been shown to pose a risk to human health and aquatic life. The degradation of petroleum hydrocarbons in water needs to consume lots of dissolved oxygen, which can worsen the water quality and generate a foul smell [2].In many countries, the content of petroleum hydrocarbon has been one of the control items in the environmental quality standard of surface water and soil. Hence, it is important to determine the types of hydrocarbons that may be present in contaminated soil and water.

Alfa Chemistry has a wealth of experience in the detection of extractable petroleum hydrocarbons, and we devote to be a world leader in the field of oil& gas analysis. We can provide a broad range of extractable petroleum hydrocarbons testing at the same time ensure the accuracy of results in a relatively short period of time using advanced instruments.

The method of extractable petroleum hydrocarbons test

At present, the determination methods of petroleum hydrocarbon mainly include weight method, infrared spectroscopy method and chromatographic method. Among them, the first two approaches are usually used to determine the content of total petroleum hydrocarbon, and gas chromatography (GC) or GC-MS are widely used to determine single components such as n-saturated alkanes in petroleum and certain types of polycyclic aromatic hydrocarbons [3-4]. Here we use GC or GC-MS method to detect the extractable petroleum hydrocarbons, which is mainly divided into two steps.

• 1. Sample Extraction Procedures

A sample submitted for EPH analysis is extracted with methylene chloride, dried over sodium sulfate, solvent exchanged into hexane, and concentrated in an apparatus. Sample cleanup and separation into aliphatic (C9-C18, C19-C36) and aromatic fractions (C11-C22) is accomplished using commercially available silica gel cartridges or prepared silica gel columns. The two individual fraction extracts are then re-concentrated and separately analyzed by a capillary column gas chromatography equipped with a flame ionization detector. In this process, the silica gel cleanup and fractionation step is a critical and highly sensitive procedure. Small changes in the volumes of eluting solvents, fractionation equipment, and fractionation techniques can significantly impact the proportion of hydrocarbons segregated in either the aliphatic or aromatic fractions. Considerable care and attention is required to ensure satisfactory results.

• 2. GC-FID Analysis

The aliphatic and aromatic hydrocarbons have different boiling point ranges between approximately 150 °C and 265 °C. In general, the branched alkanes have lower boiling points than their n-alkane counterpart, while many of the cycloalkane constituents of diesel range volatile organics have higher boiling points than their n-alkane counterpart. Hence, the chromatogram of aliphatic and aromatic compounds can be obtained by different retention time, and the concentration of aliphatic and aromatic compounds can be calculated based on their standard calibration curves.

We shall be greatly honored to provide you high-quality oil and gas tests. Feel free to contact us at any time. Our professional team will be glad to listen to your concerns and look forward to cooperating with you.

References

• P Wu, G.H. Yu, S. F. Yu. The fractional composition of petroleum [J]. Science and Technology Information, 2011, 25: 35-36．

• H. Y.ZHANG, Z WANG, S ZHOU. Determination of total petroleum hydrocarbon in environmental matrix by gas chromatography [J]. Environmental Monitoring and Forewarning, 2013, 5(2): 24-27.

• P. J. Xu, T Zhang. Quality control on the determination of 16 PHAs in soil using ASE-SPE/GC-MS [J]. Journal of Instrumental Analysis, 2012, 31(9): 1126–1131.

• Q. L. Li, X. Q. Xu. The determination of polycyclic aromatic hydrocarbons in Sediments with ASE /GC-MS[J]. Journal of InstrumentalAnalysis,2006, 25(5): 33–37.