Chasing FAME: Fatty Acid Methyl Esters detected in trace amounts

Skip to Navigation

Ezine

  • Published: Jul 1, 2016
  • Author: Ryan De Vooght-Johnson
  • Channels: Gas Chromatography
thumbnail image: Chasing FAME: Fatty Acid Methyl Esters detected in trace amounts

Bio-revolution

In a world where fossil and biofuels coexist, however, the cross contamination of conventional fuels with Fatty Acid Methyl Esters (FAMEs)—a component of biofuels—be it though accidental mixing or blatant adulteration, can compromise the very properties that make fossil fuels useful.

We are at a turning point of humanity. Our pre-industrial ancestors of the 18th century witnessed a cultural evolution that forever cemented humankind’s reliance on industry to provide for the world’s booming population. These steam-driven pioneers, however, could not have imagined what their coal-hungry contraptions would lead to.

Fast forward to the 21st century. Currently, humankind pumps carbon locked underground within the finite reserves of fossil fuels—petroleum, oil and coal—into the atmosphere with devastating consequences. Our world is becoming less hospitable year-on-year, scientists argue. Our habits or our existence must give.

‘Finite supplies of fossil fuels and concerns about their environmental impacts have led to an increase in the use of alternatively derived fuels across the globe,’ Webster and colleagues explain in the Journal of Separation Science. Biodiesel is one such alternative fuel. Synthesised by the transesterification of vegetable oils, biodiesel is renewable, emits much less carbon dioxide into the atmosphere, and can be used with existing diesel engines.

In a world where fossil and biofuels coexist, however, the cross contamination of conventional fuels with Fatty Acid Methyl Esters (FAMEs)—a component of biofuels—be it though accidental mixing or blatant adulteration, can compromise the very properties that make fossil fuels useful. Even trace levels of FAMEs, for example, compromise its stability, render it more prone to freezing, and complicate its separation from water.

Two dimensions

Current guidelines spell out that the level of FAMEs should not exceed 50 mg per kg of aviation fuel. For naval fuels, this content is much less—0.1% worldwide, or absolutely nil in Australian waters. Whilst the determination of FAME levels in aviation fuels is straightforward given the success one-dimensional gas chromatographic has in separating the ‘high volatility range of hydrocarbon’ components, the analysis of naval fuels is much more complicated.

‘Due to significant overlap of the complex hydrocarbon matrix with FAME analyses,’ the Australian researchers warn, ‘it is impossible to resolve low levels of FAME contamination in diesel fuels with conventional chromatographic separations.’ Spurred on by the current lack of suitable methods able to determine conformity to guidelines in problematic naval-fuel matrixes, Webster et al. set out to separate the co-eluents over two dimensions followed by mass spectrometry-based analyses.

Their two-dimensional separation relies on two columns: the first, a long, non-polar column ideally suited for massive separation of hydrocarbons; and the second, the only highly-polar ionic liquid phase column capable of withstanding the high temperatures needed to boil fuel components. Consequently, fuel components were separated by increasing the temperature from 35 through to 300 °C, where three ion identifiers per FAME were selectively monitored for (SRM) in a mass spectrometer. Of these three ions, the one with the greatest signal-to-noise was used for quantitation.

Adding fuel

The researchers opted to experiment with their method of ionisation on a set of military-grade naval fuel (chosen for its stringentness for nil FAME content) spiked with six FAME compounds, from 10 to 50,000 mg/mL. Ultimately, their trials found that chemical ionisation of FAMEs with methane translated to a lower limit of detection for some compounds, whereas the soft electron ionisation mode afforded an extra order of magnitude in the linear range and improved repeatability.

The breakdown of FAME levels according to individual compounds—and not just the total FAME content—will also aid authorities in isolating the source of contamination. The authors tested this on soy- and suspected-contaminated fuels. Given the tell-tale FAME profiles, the authors found that the soy-contaminated fuels mirrored the fatty acid composition of soybean oil, and even speculated that the fuel of unknown origin was adulterated with palm oil biofuels given its high C18:1 and C18:2 content.

The separation of FAMEs over two dimensions has afforded the quantitation of FAMEs up to two orders of magnitude lower than current methods. ‘This analysis,’ the authors conclude, ‘will be valuable for determining trace amounts of biodiesel contamination in diesel fuel matrices where the presence of oxygenated compounds can be detrimental to engine performance.’

Related Links

J. Sep. Sci., 2016. Webster et al., Quantification of trace fatty acid methyl esters in diesel fuel by using multidimensional gas chromatography with electron and chemical ionization mass spectrometry.

Article by Ryan De Vooght-Johnson

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

Follow us on Twitter!

Social Links

Share This Links

Bookmark and Share

Microsites

Suppliers Selection
Societies Selection

Banner Ad

Click here to see
all job opportunities

Copyright Information

Interested in spectroscopy? Visit our sister site spectroscopyNOW.com

Copyright © 2017 John Wiley & Sons, Inc. All Rights Reserved