GC Analysis of Primary Fatty Acid Amides in Animal Fat

Waste animal fats represent a very attractive feedstock for biodiesel production. Primary fatty acid amides (PFAA) are a class or bioactive signaling lipids found in mammalian organisms, as well as several plant families. Waste animal fat coming from rendering plants can obtain up to 2.0% PFAA. After the conversion process they pose a risk in the final biodiesel as they can lead to deposits in storage tanks or plug fuel filters. In this paper, a method for efficient separation and quantification of PFAAs in waste animal fat is presented. The method consists of separation of PFAAs via solid phase extraction (SPE) using cartridges with 60 angstrom silica as stationary phase. The most effective eluents are determined to be hexane: ethyl acetate followed by chloroform: 2-propanol. The isolated PFAAs are identified and quantified via gas chromatography-flame ionization detector (GC-FID) using nonadecanoic acid amide as an internal standard. The recovery of PFAAs in lard as matrix is determined to be around 100%. Six real samples are analyzed for the content of PFAAs leading to concentrations between 0.04% and 1%. Additionally, the limits of detection and quantification are determined to be 0.002% and 0.005%, respectively. Practical applications: The developed method is an efficient tool for characterization and determination of primary fatty acid amides in animal fat used as starting material for biodiesel production. The developed simple and efficient separation of PFAA via SPE and GC-FID analysis without derivatization can also be applied to other biological fat samples, such as fat tissue, and plasma samples or microbial oils.