What is Fatty Acid Methyl Ester?

Fatty acid methyl esters (FAME), sometimes referred to as methyl esters, are compounds usually derived through transesterification reactions and are the main components of the biodiesel process. While most methyl esters are derived from plant feedstocks such as soybean oil, canola oil or palm kernel oil, there are also some varieties derived from tallow.

In biochemistry, to analyze the content of various fatty acids in a sample, lipids in the sample are extracted and modified into FAMEs by methylation reagents such as BSTFA, which can be separated, content determined and isotopic abundance judged by gas chromatography, etc.

FAME can be used in place of petroleum diesel in internal combustion engines and is known for its low emissions and biodegradability. It is often used as an alternative to diesel fuel in transportation, power generation and industrial applications. FAMEs are also widely used in the synthesis of advanced surfactants, as solvents for advanced lubricants, emulsifier products, fragrances, and dye intermediates.

Fatty acid methyl ester production via ferric sulfate catalyzed interesterification (Yuan Tian et al., 2018).

What is the Structure of Fatty Acid Methyl Ester?

Fatty acid methyl esters (FAMEs) are a type of derivative of fatty acids. Each FAME molecule contains a long hydrocarbon chain, which is made up of a varying number of carbon atoms (typically between 8 and 24). At one end of the chain, there is a carboxyl group, which is connected to a methyl ester group at the other end.

More specifically, the hydrocarbon chain of a FAME consists of a series of carbon-carbon single bonds, with one carbon atom at the beginning of the chain (known as the alpha carbon) and a terminal methyl group at the end of the chain (known as the omega carbon). Each carbon atom in the chain is also bonded to two hydrogen atoms.

The carboxyl group, which is located at the alpha end of the chain, consists of a carbon atom that is double bonded to an oxygen atom (known as the carbonyl group) and also bonded to a hydroxyl group (-OH) through a single bond. The methyl ester group, which is located at the omega end of the chain, consists of a carbon atom that is bonded to three hydrogen atoms and a second oxygen atom (via a double bond), with the overall molecular formula RCOOCH3 (where R represents the hydrocarbon chain).

Overall, the structure of a FAME can vary depending on the length and degree of unsaturation of the hydrocarbon chain, but the basic structure consists of a carboxyl group at one end and a methyl ester group at the other end of a long hydrocarbon chain.

What are the Analytical Methods for Fatty Acid Methyl Ester?

Fatty acid methyl esters (FAMEs) are important biomolecules with a variety of applications in nutrition, biofuel production and cosmetics. Analytical methods for FAMEs play a key role in the characterization and quantification of these compounds. Currently, there are several methods commonly used for the analysis of FAMEs as follows

Mass spectrometry (MS)

Mass spectrometry (MS) is a powerful technique for the identification and quantification of FAMEs. In MS, FAME molecules are ionized in a vacuum and the resulting fragments are detected by a detector. MS can provide accurate and precise information about the molecular weight, composition and structure of FAMEs. Compared to GC and HPLC, MS is a more specialized technique, but highly sensitive and accurate.

Gas chromatography (GC)

Gas chromatography (GC) is the most commonly used method for the analysis of FAMEs. In this method, FAMEs are separated according to their volatility by injecting the sample into a gas chromatographic column filled with a stationary phase. The FAMEs are eluted from the column and detected by a flame ionization detector (FID) or mass spectrometer (MS). FID is more frequently used because of its low cost and high sensitivity. GC is popular among analysts because it provides a simple and rapid method with a high degree of accuracy and precision.

Comparisons of analysis of fatty acid methyl ester (FAME) of microalgae by chromatographic techniques (Calle Niemi et al., 2019).

High Performance Liquid Chromatography (HPLC)

High performance liquid chromatography (HPLC) is another popular technique for the analysis of FAMEs. In this method, FAMEs are separated by injecting the sample into a column filled with a stationary phase, and then the FAMEs are washed out of the column with a mobile phase. FAMEs are detected by UV-Vis spectrophotometer or mass spectrometer. High performance liquid chromatography in the analysis of FAMEs can separate highly complex mixtures and analyze non-derivatized samples.

Nuclear magnetic resonance spectroscopy (NMR)

Nuclear magnetic resonance (NMR) spectroscopy is a technique used to analyze FAMEs, providing information about the structure and composition of biomolecules. In NMR, molecules are placed in a magnetic field, which causes the nuclei of some atoms to resonate. This information is detected and processed to provide a spectrum. NMR is a non-destructive technique that requires only a small amount of sample and can provide highly accurate and quantitative data on the composition of fatty acids.

Gas chromatography is the most commonly used method because it is simple, rapid, sensitive and cost effective. HPLC is a more specialized method for analyzing complex mixtures. Mass spectrometry provides highly accurate and precise molecular information, and NMR provides detailed structural information. Combining these methods can provide complementary information and enhance the characterization of FAMEs.

References

1. Yuan Tian, Junwei Xiang, et al. "Fatty acid methyl ester production via ferric sulfate catalyzed interesterification" Biomass and Bioenergy. 115(2018): 82-87.
2. Calle Niemi, Sandra Lage, et al. "Comparisons of analysis of fatty acid methyl ester (FAME) of microalgae by chromatographic techniques" Algal Research. 39(2019): 101449.

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