Petroleum products contain a complex mixture of aliphatic and aromatic components. The composition of hydrocarbons varies depending on the source, e.g. crude oil versus refined products. Not all components pose the same amount of health risk. Particularly the amount of polycyclic aromatic hydrocarbons (PAH) needs to be determined accurately. In order to properly separate both aliphatic and aromatic fractions, a pre-fractionation with silica gel is carried out. The manual method is tedious and requires a very good technique to obtain good recovery for the volatile PAH.

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Automating the Fractionation of Extractable Petroleum
Hydrocarbons with a Scaled Down Silica-Gel Cartridge
Roel Wu�ts, Jef Leemans and Joeri Vercammen
j.vercammen@is-x.com
www.is-x.com
Petroleum products contain a complex mixture of aliphatic and aromatic components. The
composition of hydrocarbons varies depending on the source, e.g. crude oil versus refined
products. Not all components pose the same amount of health risk. Particularly the amount
of polycyclic aromatic hydrocarbons (PAH) needs to be determined accurately.
In order to properly separate both aliphatic and aromatic fractions, a pre-fractionation
with silica gel is carried out. The manual method is tedious and requires a very good
technique to obtain good recovery for the volatile PAH.
Fractionation is carried out automatically using the SmartPrep Extractor. Recoveries are acceptable for all
components and range between 75% and 120% voor five replicate fractionations. Breakthrough of naphthalene
is < 5%. Precisions are situated between 3 and 20%. A post run system flush is applied to reduce carry-over.
Commercial SmartPrep Extractor (Horizon Technology) equipped with 6 mL silica gel cartridges (2.5 g).
Cartridge is PTFE coated to eliminate cross contamination from hydrocarbon extractables and
plasticizers. Custom sequence based on EPH reference methods*.
Goals:
- Process six extracts
- Less than 5% breakthrough for naphthalene
- Maximum recoveries for aliphatics and aromatics
- High precision
- Robust
- No carry-over between samples
* Consecutive elution with hexane (aliphatic phase) and hexane/DCM (aromatic phase).
2.3%
Naphthalene breakthrough
82.4%
C24 recovery
118.1%
C9 recovery
ANT recovery
73.8%
I(123-cd)PY recovery
111.6%
Aliphatic fraction
Aromatic fraction
0 100
0 100
Typical chromatograms Minimal and maximal analyte recoveries (n=5)