Separation, quantitative determination, and fatty-acid profiling of monoglycerides in Fatty-Acid Methyl Esters (FAME) using an on-line, hyphenated technique based on AMD-FDIC- ESI-MS

Researcher: 
Jarne Lardiés, Carmen
Congress: 
International Symposium for Thin-Layer Chromatography
Participation type: 
Póster
Year: 
2014
Location: 
Lyon (Francia)

FAME is a biodiesel obtained from vegetal or animal oils through esterification and transesterification processes, which is used as a total or partial substitute for petroleum derived-diesel. Monoglycerides are one class of the impurities coming from an incomplete esterification reaction. Due to their high fusion point and low solubility at low temperatures, monoglycerides can produce deposits in motor engines. The maximum concentration of monoglycerides tolerated in FAME by UNE-EN14214:2013 standard is 0.8 wt%.
We evaluate here the determination by HPTLC of monoglycerides in 9 FAMEs from vegetal and animal origins. Monoglycerides have been separated from other FAME components (fatty acids, diglycerides, triglycerides and fatty acid-methyl esters) using a 3-step AMD separation based on a t-butyl methyl ether-dichloromethane-n-heptane gradient, over a total migration step of 90 mm, in one hour. Densitometric Fluorescence Detection by Intensity Changes and quantitative determination of monoglycerides have been carried out by plate post-impregnation using primuline (200 ppm) by excitation at 365 nm. Identification of monoglycerides was done in FDIC by using glyceryl stearate as standard, and also by ESI-MS, after an on-line extraction of the peak using a head-elution based TLC-MS interface. Moreover ESI-MS provides the fatty acid profile of the corresponding FAME-derived monoglyceride.
One plate per analyzed FAME was used. In each plate, the corresponding FAME was applied on triplicate (three 12 mm-bands, 2500 µg each), together with 10 sample bands corresponding to different sample loads of the standard. Intra-plate and inter-plate calibrations show adequate repeatability, and a good sensitivity to determine monoglycerides far below the limit required by the UNE standard.

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