January 11, 2013

A Novel Petrochemistry Solution:
SARA Fractionation of Crude Oil Using an
Adaptable Gilson MPLC System
Authored By:
Freddy Moy and Fabrice Mangani – Gilson BV France & Toni R. Hofhine – Gilson, Inc.

Technical Note 0312

Overview
Petroleum consists of a complex hydrocarbon mixture, result of a slow process ofnature (thousands of years) issued from sediment deposits which contained
microorganisms, animals and plants. Due to the successive sedimentary rock layers
accumulation, under Heat and Pressure, organic matter has been transformed intoKerogen and finally into Oil and Gas.
Crude oil is mainly composed by hydrocarbons and derived organic sulfur, nitrogen,oxygen and organometallic, composition which depends directly on location, ageand depth. The hydrocarbons in oil can be classified into four main classes based onpolarity and solubility (see Figure 1):-Saturated (alkanes and cycloparafinns)
Aromatics (hydrocarbons, mono, di and polyaromatic)
Resins (polar molecules with heteroatoms N,O,S)
Asphaltenes (similar to the resins with higher molecular weight andpolyaromatic core)

Figure 1:
Structures of four mainhydrocarbon classes(image from ScienceDirect.com)

Gilson, Inc. World Headquarters
Middleton, WI 53562 USA
Telephone: 800‐445‐7661

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January 11, 2013

Oil composition determination constitutes a key point from geochemists to therefiners, from the rock degradation degree to the amount of heavy organic dissolved
and suspended solids precipitation. Results from SARA analysis are used as a quality
indicator of oils and bitumens. Analysis results of the SARA fraction proportions arealso used to calculate the asphaltene stability within the oil.
Final SARA analysis is not possible without sample preparation prior to a variety of
published analysis methods, such as GC, GC/MS and Isotopes analysis. Gilson has
developed a novel petrochemistry solution to enable SARA fractionation (i.e. samplepreparation) using an adaptable Gilson MPLC (Medium Pressure Liquid
Chromatography) System.

Materials & Methods
The Gilson MPLC System (see Figure 2) is dedicated to the separation and sample
preparation of deasphatened solution (maltene) obtained after nPentane addition in
Crude oil and asphaltene fraction precipitation. Maltene extract has separated with
our MPLC (Medium Pressure Liquid Chromatography) system into 3 fractions:
Saturates, Aromatics, Resins. Up to 100 mg of extract can be injected and separated
to allow for both the traditional gravimetric quantification of each fraction and also
additional final analysis (as described above) separate from the MPLC system.

UV 156

Figure 2: Gilson MPLC System for SARA Fractionation of Crude Oil
Gilson, Inc. World Headquarters
Middleton, WI 53562 USA
Telephone: 800‐445‐7661

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January 11, 2013

The Gilson MPLC System Description for SARA Fractionation in Crude Oil:
- GX ‐271 Liquid Handler with Dilutor 402:
o aspirates and injects samples into an injection loop via two
independent collection valves
o all fractions are collected into evaporation flasks through thefraction valve on the GX‐271 Liquid Handler- Two 307 Single Piston Isocratic Mobile Phase Pumps (Pumps A and B) areused to generate the process range mobile phase flow rates (8‐10 ml/min):o flows through silica gel pre‐columns and an activated silica
analytical column are implemented
o prevent damage of the analytical column during the SAR
separation and maintain good separation reproducibility
between sample injections, the Gilson MPLC System avoids any
presence of polar solvent through the analytical column
 pump A is dedicated to the conditioning and fraction
collection step of Saturates and Aromatics
 pump B allows the fraction collection of resins throughthe final back‐flushing of pre‐columns
 for additional security, the mobile phase from Pump A
can be passed through an Alumina Column- Five VALVEMATE® II column switching valves provide full automation:- Valve A:
selects up to 6 different solvents for the rinsing steps andfor the resins elution steps.
- Valve B :isolates the analytical column during resins elution steps- Valve C & C’: provide automatic pre‐column selection according tocurrent sample injected, and up to 6 samples can beprepared during one application sequence- Valve D :provides analytical column back‐flushing for aromatics
fraction collection- Refractive Index Detector Gilson 156 UV detector:
o validates the SAR separation and fraction collection timing

Gilson, Inc. World Headquarters
Middleton, WI 53562 USATelephone: 800‐445‐7661

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January 11, 2013

The Typical Gilson MPLC Sample Sequence (see Figure 3):
1. Pre‐columns (silica gel) and analytical column (activated silica) areconditioned with Pump A.
2. After injection (typically 1ml of sample), the sample passes through thepre‐column and analytical column in a ‘serial’ configuration using Pump A
The saturates are collected.
3. After Valve D switching and the analytical column back‐flushing, aromatics
are automatically collected into another evaporation flask.
4. After Pump A stops and Valve B switching isolates the analytical column, theresins fraction is collected from the pre column in ‘back‐flush’ mode withPump B flow rate and resin elution solvent selection (Valve A) into anotherevaporation flask via a 2nd collection valve.
5. The Valve C and C’ are incremented by one position and placed in ‘by‐pass’
position. After Rinsing solvent selection on Valve A, the system is rinsing
before the next sample injection.

Figure 3: Gilson TRILUTION LC v2.1 Sample Sequence (Operations List shown)

Gilson, Inc. World Headquarters
Middleton, WI 53562 USA
Telephone: 800‐445‐7661

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January 11, 2013

Technical Summary
SARA fractionation of crude oil using the Gilson MPLC System produces highly
desirable chromatography and reproducible separations. RSD retention times areapproximately 2%. Excellent recoveries of each fraction of the SAR separation were>98%, with a CV around 0.6% (see Figure 4).

Figure 4: Gilson MPLC System Results ‐ Test Mixture Injection(from left to right: decane, decene‐1, deca‐1,9 diene, n‐butylbenzene)

Multiple columns allow for fraction collection of SAR using the adaptable MPLC
platform. Up to 100 mg of deasphatened sample extract can be injected andseparated using the Gilson MPLC System. Traditional gravimetric quantification ofeach fraction can be performed, as well as final additional analysis as a result of thesample preparation.

Gilson, Inc. World Headquarters
Middleton, WI 53562 USA
Telephone: 800‐445‐7661

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Questions? Please Contact Us
If you have application questions related to this technical note or if you areinterested in further information on the Gilson system configurations discussed,
please feel free to contact us:
Gilson Applications (within the Gilson Knowledge Center Department)
Email: applications@gilson.com
Phone: 1‐800‐445‐7661 OR 1‐608‐836‐1551

Gilson, Inc. World Headquarters
Middleton, WI 53562 USA
Telephone: 800‐445‐7661

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