Application of High Performance-TLC coupled to Electrospray (ESI) Ionization Tandem Mass Spectrometry for structural analysis of complex lipid-based samples
HPTLC experienced a great instrumental development in recent years. The modularity
of its basic steps, i.e. sample application, chromatographic development and detection, their automation and computer control confer HPTLC a high degree of flexibility and reliability. A HPTLC-based hyphenation system has been used here which consists of: a spray-on sample applicator; Automated Multiple Development (AMD), a technique that uses solvent gradient elution; densitometric detection (UV and fluorescence); and on line coupling with an ESI-quadrupole ion trap mass spectrometer. Therefore, MS/MS (MSn) spectra of lipids can be obtained directly from the chromatographic plate through
automatic extraction and direct transfer of separated peaks using an elution-based interface. In this talk I will present two examples to illustrate its application. Conditions have been selected for obtaining composition profiles and structural individual identification of mono-, di- and tri-acylglycerides through their MS/MS spectra (in ESI-positive ion mode) and fatty acids (in ESI-negative ion mode), as impurities of FAME biodiesel. Likewise, using the above system, molecular species of sphingomyelins (SMs) have been unequivocally identified in human plasma (ESI-positive). .SMs are the most
abundant sphingolipids in human plasma and their molecular species are related to Niemann-Pick disorder, a Lysosomal Storage Disease. The fact that only the desired peaks on the plate can be transferred to the MS instrument is of particular interest for obtaining rapid relevant information about the sample. This, together with the high sample throughput and low solvent consumption leads to significant savings in the cost of analysis.