Extractable Petroleum Hydrocarbons (EPH) methodology was recently released by the New Jersey Department of Environmental Protection (NJDEP) to replace the Total Petroleum Hydrocarbons (TPH) method based on Freon 113 extraction and IR. This method allows aliphatic and aromatic C9-C44 hydrocarbons to be measured separately. It can be used for quantitative analysis of environmental samples (water, soil, sediment and sludge) for residues of crude oils, diesel, sludge and many other types.
Silica gel cleanup and fractionation of aliphaticsand aromatics is a critical and sensitive step in this method. Slight changes, such as the volumes of eluting solvents used, fractionation equipment (including the preparation of the silica gel columns) and fractionation techniques, will have tremendous impact on the proportion of the hydrocarbons separated into their respective aliphatic and aromatic fractions.
Here we present a method based on an automated sample processing station and commercial silica cartridges for rapid, reproducible and efficient fractionation procedure.
Figure 1 EPH Method Workflow
10 Gram soil sample was mixed with pelletized diatomaceous earth, a drying agent, and was loaded into an extraction cell. After adding 100 μL of 1000 ppm surrogate mix (1-chlorooctadecane and o-terphenyl), sample was heated and pressurized with methylenechloride. Extract was collected, dried, concentrated to 1 mL and solvent exchanged to hexane.
With the addition of 1 mL 100 ppm fractionation surrogates mix in hexane (2-bromonaphthlene and 2-fluorobiphenyl), 1 mL extract was fractionated through a 5 g/25 mL silica cartridge (Bonna-Agela Technologies, P/N SI500025-30). Recovered fractions of the aliphatics and aromatics were then concentrated to 1 mL and analyzed separately by Gas Chromatography/ Flame Ionization Detector (GC/FID). A method blank (MB) was done in the same way except that 10 g diatomaceous earth was used to monitor the contamination of the extraction procedure. Method blank spike (MBS) and duplicate (MBSD) analysis were also performed similarly but in addition to the 100 μL surrogate, 100 μL of the 1000 ppm spike mix (all of the aliphatic and aromatic compounds) was added before fractionation.
Results and Discussion
200 ppm Fractionating Check Solution (FCS) 1 was used to monitor the fractionation efficiency of the silica gel and establish the optimum hexane volume required to efficiently elute the aliphatic fraction without significant aromatic breakthrough (naphthalene and 2-methylnaphthalene were not detected in aliphatic fraction, data now shown).
Figure 2 Representative FCS Gas Chromatograms
Figure 3 Quantitation report of a real soil sample
Cleanert® EPH performed high fractionation capability with improved reproducibility to extract the Petroleum Hydrocarbons in soil samples.
5 g / 25 mL