Efficient and sensitive method for the quantification of saturated monoacylglycerols in biodiesel by gas chromatography–mass spectrometry

Abstract

The experimental approach of this work was to develop a new method for the quantification of saturated MAGs in biodiesel using GC–MS. The method was established on a 30 m 5% phenyl phase column and ensured satisfying separation of the target MAGs. The quantification of the saturated MAGs was carried out in single ion monitoring (SIM) mode using the quantitation ions for the target MAGs: m/z 218 (2‐C16:0), m/z 371 (1‐C16:0), m/z 385 (1‐C17:0), and 399 (1‐C18:0) as well as m/z 413 for 1‐C19:0, serving as an internal standard (IS). The analytical procedure involved mixing the biodiesel sample with the IS and a silylating agent before applying GC–MS analysis. Response factors for the individual target MAGs related to the IS were determined. Prior to the quantification of saturated MAGs in real biodiesel samples, derived from used cooking oil (UCO) and waste animal fats (WAF), the linearity (R2>0.99) and the limits of detection and quantification (LOD: 8–20 ng/g, LOQ: 26–61 ng/g) of the method were determined.Practical applications: The European Committee for Standardization (CEN) contemplates to establish a limit value specifically for saturated MAGs in biodiesel, primarily requiring a specific analysis method. At present, there is no suitable test method for the determination of saturated monoglycerol content in FAME. Therefore, the approach of this work was to develop a new method for the quantification of saturated MAGs in biodiesel using GC–MS. In contrast to the currently valid European standard method EN 14105 for the determination of free glycerol, mono‐, di‐ (MAGs, DAGs), and triacylglycerols (TAGs), this new method features a very high sensitivity and enables the exclusion of interfering substances, both due to performing the analysis in single ion monitoring mode (SIM).