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Alternative Methods to Determine Aromatics and Olefins in Fuels

ASTM D1840 – Standard Test Method for Naphthalene Hydrocarbons in Aviation Turbine Fuels by Ultraviolet Spectrophotometry

Year approved: 1961
Separation method: none
Level of complexity: low
Materials used: iso-octane; pipettes; lens paper
Classes determined: di-aromatics
Speciation: none
Range:  Naphthalenes: min Vol% .03, max Vol% 4.25
Sample types: aviation fuel

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Pros

$mo
  • Relatively simple setup without a lot of steps or consumables
  • Low cost

Cons

$mo
  • Method can only determine multi-aromatic compounds
  • Low overall sensitivity in order to mitigate mono-aromatic interference, this method works at a non-optimum wavelength
  • Can not provide qualitative information or speciation, only ``total naphthalene content``
  • Has known interfering compounds that can contribute up to 2% error each

UV-VIS Process

Image courtesy of: LINK

ASTM D5186 – Standard Test Method for Determination of the Aromatic Content and Polynuclear Aromatic Content of Diesel Fuels and Aviation Turbine Fuels by Supercritical Fluid Chromatography

Year approved: 1991
Separation method: supercritical fluid chromatography
Level of complexity: low
Materials used: supercritical CO2; single column, but requires an SFC system
Classes determined: poly-aromatics and total aromatics
Range: Monoaromatics: min Mass% 1, max Mass% 75; Polyaromatics min Mass% 0.5, max Mass% 50
Speciation: none
Sample types: diesel and aviation fuel

d5186

Pros

$mo
  • Relatively simple setup without a lot of steps or consumables
  • Green certified (environmentally friendly)

Cons

$mo
  • Method can only determine aromatics
  • No precision statement for jet fuel
  • Method does not clearly specify how to differentiate aromatics from poly-aromatics
  • Moderately priced

ASTM D6379 – Standard Test Method for Determination of Aromatic Hydrocarbon Types in Aviation Fuels and Petroleum Distillates—High Performance Liquid Chromatography Method with Refractive Index Detection

Equivalent: IP436

Year approved: 1999
Separation method: high performance liquid chromatophraphy
Level of complexity: moderate to high
Materials used: heptane; LC column
Classes determined: aromatics and di-aromatics
Speciation: none
Range:  Monoaromatics min Mass% 10, max Mass% 25; Polyaromatics min Mass% 0, max Mass% 7
Sample types: aviation fuels; petroleum distillates
Alternative method in: D1655 for jet fuel standard and Dev Standard 9191

d6379

Pros

$mo
  • Provides clear separation of mono-aromatic hydrocarbons and di-aromatic hydrocarbons

Cons

$mo
  • This method can only determine aromatics
  • This method is not widely available and expensive to run
  • Refractometer is prone to interference from slight environmental changes
  • Produces a large amount of solvent waste
  • Only measures % mass; must use a special calibration to get volume %; Precision statement only in mass%

HPLC Process

HPLC process

Image courtesy of: https://microbenotes.com/high-performance-liquid-chromatography-hplc/ 

ASTM D6550 – Standard Test Method for Determination of Olefin Content of Gasolines by Supercritical-Fluid Chromatography

Year approved: 2000
Separation method: none
Level of complexity: moderate — high
Materials used: supercritical CO2; 2 valves and 2 columns
Classes determined: olefins and aromatics
Speciation: none
Range:  Olefins min Mass% 1, max Mass% 25
Sample types: gasoline (correlates to D1319)

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Pros

$mo
  • Green certified (environmentally friendly)
  • EPA alternative approved method

Cons

$mo
  • Moderately complex setup consisting of 2 valves and 2 columns
  • This method is limited to gasoline
  • Requires cylinders of CO2 to be stored regularly

Photo courtesy of: http://www.astm.org/cgi-bin/resolver.cgi?D6550

ASTM D6839 – Standard Test Method for Hydrocarbon Types, Oxygenated Compounds, and Benzene in Spark Ignition Engine Fuels by Gas Chromatography

Equivalent: ISO 22854

Year approved: 2002
Separation method: multidimensional GC
Level of complexity: high
Materials used: inert carrier gas; 5 valves, 3 traps, & 4 columns; some setups have 7 valves, 3 traps, and 5 columns
Classes determined: PIONA, oxygenates
Speciation: benzene, total oxygenates, E85
Sample types: spark ignition fuels

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Pros

$mo
  • Gas Chromatography (GC) is a familiar technology found in many modern laboratories
  • D1319 equivalency

Cons

$mo
  • Complex setup with many different equipment pieces
  • If needing to change between different methods, recalibration must be done
  • Tuning needs to be adjusted depending on relative olefin content
  • Takes a high level skilled operator to run successfully
  • High cost

Reformulyzer Process

Photo Courtesy of: https://www.azom.com/article.aspx?ArticleID=10679

ASTM D8071 – Determination of Hydrocarbon Group Types and Select Hydrocarbon and Oxygenate Compounds in automotive Spark-Ignition Engine Fuel Using Gas Chromatography with Vacuum Ultraviolet Absorption Spectroscopy Detection (GC-VUV)

Year approved: 2017
Separation method: Single column GC
Level of complexity: Low – moderate
Materials used: inert carrier/purge gas; single column, no valves or traps
Classes determined: PIONA, oxygenates
Speciation: oxygenates and BTEX
Sample types: spark ignition fuels

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Pros

$mo
  • Method can determine PIONA classes plus oxygenates
  • Compatible with any GC, a technology widely available
  • Direct detection technique, it does not rely on retention time for analyte identification
  • Clearly speciates many compounds of interest
  • Low total cost of ownership
  • Calibration Free
  • Data processing is automatic and not measured by a human
  • Uses spectra to deconvolve coellutions

Cons

$mo
  • Relatively new technology
  • Does not have a precision statement

GC-VUV Process Gasoline

VGA Technical

Photo Courtesy of: https://vuvanalytics.com/

ASTM D8267 GC-VUV for Jet Fuels; Determination of Total Aromatic, Monoaromatic and Diaromatic Content of Aviation Fuels using GC-VUV

Year approved: 2019-a
Separation method: Single column GC
Level of complexity: Low – moderate
Materials used: inert carrier/purge gas; single column, no valves or traps
Classes determined: di-aromatics
Speciation: n/a
Sample types: jet fuels

Embed from Getty Images

Pros

$mo
  • Compatible with any GC, a widely available technology
  • Direct detection technique, doesn't rely on retention time for analyte identification
  • Low level of complexity enables robustness
  • Same hardware and set up as ASTM D8071
  • Low total cost of ownership

Cons

$mo
  • ASTM US Spec Approval only

GC-VUV Process Jet Fuels

VGA Technical

Photo Courtesy of: https://vuvanalytics.com/

Analysis of Diesel with GC-VUV

Year approved: pending
Separation method: Single column GC
Level of complexity:  moderate
Materials used: inert carrier/purge gas; single column, no valves or traps
Classes determined: Aromatics, Saturates, PAHs, Mono, Di, Tri+ Aromatics
Speciation: n/a
Sample types: jet fuels