Geoquimica

Organic Geochemistry
Organic Geochemistry 38 (2007) 1235–1250 www.elsevier.com/locate/orggeochem

Rapid small-scale separation of saturate, aromatic and polar components in petroleum
Trevor P. Bastow
a b

a,*

, Ben G.K. van Aarssen

b,1

, Dale Lang

a,b

CSIRO Land and Water, Private Bag No. 5, PO Wembley, Perth, WA 6913, Australia Centre for Applied Organic Geochemistry,Curtin University of Technology, P.O. Box U1987, Perth, WA 6845, Australia Received 8 January 2007; received in revised form 12 March 2007; accepted 16 March 2007 Available online 24 March 2007

Abstract A rapid small-scale method for the separation and analysis of saturate, aromatic and polar components from petroleum is described using silica gel liquid chromatography and GC–MS techniques. Crudeoil samples rich in long chain alkylbenzenes and mono-aromatic steranes were used to demonstrate that complete separation can be obtained using disposable glassware such as Pasteur pipettes and minimal amounts of solvents and silica gel, with sample sizes up to 20 mg. This method affords rapid sample processing suitable for routine use in petroleum geochemistry and environmental forensics. Ó 2007Elsevier Ltd. All rights reserved.

1. Introduction Analysis of saturate, aromatic and polar components of petroleum is commonly used in petroleum geochemistry (Murphy, 1969; Seifert, 1977; Jiang et al., 2000; Peters et al., 2005) and environmental forensics (Moldowan et al., 1995; Peters et al., 2005). The separation of these components into individual fractions is required often because compoundsof interest, such as steranes, hopanes, phenanthrenes, and aromatic steranes, are often present in trace quantities compared to the bulk of the sample and must be enriched before they can
* Corresponding author. Tel.: +61 8 9333 6128; fax: +61 8 9333 6211. E-mail address: Trevor.Bastow@csiro.au (T.P. Bastow). 1 Present address: Chevron Australia Pty Ltd., 250 Street, Georges Terrace, Perth, WA6000, Australia.

be accurately analysed (Peters et al., 2005). These types of separations are also useful when characterising samples with large unresolved complex mixtures (UCMs) that are typical of biodegraded petroleum and can be difficult to characterise using a gas chromatograph-flame ionising detector (GCFID) or gas chromatograph–mass spectrometer (GC–MS) alone. Several techniques have beenapplied to separate saturate, aromatic and polar components including thin layer chromatography (TLC), open column chromatography, high-performance liquid chromatography (HPLC) (Murphy, 1969; Peters et al., 2005), medium pressure liquid chromatography (MPLC) (Radke et al., 1980) and more recently, solid phase extraction (SPE; Bennett and Larter, 2000). Of these, open column chromatography and HPLCare the most commonly used in organic geochemistry applications (Peters et al., 2005).

0146-6380/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.orggeochem.2007.03.004

1236

T.P. Bastow et al. / Organic Geochemistry 38 (2007) 1235–1250

HPLC methods provide good separation of saturate, aromatic and polar components as well as separation of mono-, di- andtriaromatic components (Peters et al., 2005). HPLC methods commonly use a silica column. The saturate and aromatic fractions are eluted using hexane and the polar fraction using methylene chloride (Peters et al., 2005). An advantage of using HPLC is that it can be computer controlled and so allows for the preparative separation of hydrocarbons to be fully automated. This reduces some of the sometimesprohibitive manpower requirements associated with large-scale liquid chromatography where many samples have to be analysed. Automation has been achieved using medium-pressure liquid chromatography (MPLC) as well as HPLC (Radke et al., 1980; Peters et al., 2005), although there are still considerable instrument costs and solvent volumes used. Open column liquid chromatography methods are used...