Separation and profiling of monoglycerides in biodiesel using a hyphenated technique based on high-performance thin-layer chromatography
Monoglycerides are one class of impurities in biodiesel (BX) that can lead to deposits in engines. In this work, they have been separated as a compound class in BX from B5 to B100, using a hyphenated High-Performance, Thin-Layer Chromatography based technique on a unique silica gel plate.
Hyphenation combines sequential steps of BX separation, densitometric detection of separated peaks, and on-line peak transferring to a mass spectrometer. A gradient separation was performed by Automated Multiple Development (AMD), followed by a post-chromatographic impregnation with primuline before densitometry detection. Therefore, chromatograms correspond to fluorescence detection by intensity changes (FDIC) of primuline in the presence of the components of BX.
The final step of hyphenation has been an on-line transfer of the peak of monoglycerides from the primuline-impregnated plate to an ESI mass spectrometer, using an elution-based interface. ESI-MS spectra provides unequivocal identification of monoglycerides, and also a qualitative profiling of monoglyceride composition.