Glycerol and monoglycerides determination in biodiesel methyl ester from palm oil using gas chromatography

Abstract

Monoglycerides and glycerol are by-products contaminants, after transesterification, in biodiesel that can lead to severe operational and engine problems such as wax precipitation, filter plugging and engine deposits. Therefore, strict regulations have been made, and accurate quality control is required. In this work, levels of monoglycerides and glycerol were determined using gas chromatography (GC) equipment with flame ionization detector (FID) refers to standard methods ASTM D6584 and EN 14105. However, the monoglycerides determination still needs firmness and validation to develop standard calibration series to fit the constituent fatty acid components of the feedstock used. This paper shows three fatty acids, i.e., monoolein, monopalmitin, and monostearin, as major components in palm-based biodiesel, which would be prepared as standard calibration and determined from commercial biodiesel samples in the determination of monoglyceride levels accurately and thoroughly. The result shows that standard solutions produce a curve with high linearity; it was above 0.998 (for free glycerol, monopalmitin, monoolein, and monostearin) and its accuracy values were >95%. However, the result for eight commercial biodiesel samples in Indonesia had a range of 0.23-0.54% w/w for total monoglycerides, 0.07 to 0.14 (% w/w) for total glycerol, and < 0.01% w/w for free glycerol, which was fulfilling to the ASTM D6751 and EN 14214 specification requirements.