Determination of Polyunsaturated Fatty Esters (PUFA) in Biodiesel by GC/GC-MS and 1H-NMR Techniques

In the present work, methods based on Gas Chromatography (GC), Gas Chromatography-Mass Spectrometry (GC-MS) and H-1-NMR techniques was developed for the characterization and estimation of Polyunsaturated Fatty Esters (PUFA) in biodiesel. The GC method enables the separation, identification and estimation of these polyunsaturated fatty acid methyl esters to be carried out using a highly polar capillary column (100% cyanopropyl silicon). GC-MS was utilized for unambiguous identification and estimation of esters and isomers present in biodiesel. The estimation of PUFA content is important because PUFA content is a part of the EN 14214 specifications of biodiesel. There is no existing standard method for the estimation of total PUFA content in biodiesel. The developed GC method also quantifies EPA and DHA (C20:5 and C22:6) fatty acid methyl esters which can be used as markers for the estimation of fish oil biodiesel. The presence of EPA and DHA indicates the contamination of fish oil in biodiesel. Further, the H-1-NMR technique has also been employed to identify and estimate PUFA containing a parts per thousand yen3 double bonds. The PUFA content was estimated from the integral intensities of the chemical shift region corresponding to all type of double bonds in the H-1-NMR spectra. Based on the developed method, GC fingerprinting of various biodiesel samples was carried out to estimate a PUFA content as low as 1,000 ppm.