Liquid chromatography-high resolution mass spectrometer for metabolomics and identification of antimicrobial compounds

• Subject Area: Analytical Chemistry ; Biological and Biomimetic Chemistry
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 533231379

Mass spectrometry in combination with liquid chromatography is one of the most powerful analytical tools as it combines high specificity with superior sensitivity and its applicability for most compounds, including non-volatiles and even thermosensitive ones. A number of types of mass spectrometers are available which have specific advantages and weaknesses. Triple quadrupole mass spectrometers have a high sensitivity and linear range and are therefore ideal for trace analysis of known compounds (targeted analysis). However, they are less useful for non-targeted analysis and for identification of unknown compounds since they have only a resolution of 1 mass unit. Thus, the elemental composition of a compound and the molecular formula cannot be determined. In contrast, high resolution mass spectrometry allows the determination of the molecular mass typically to the 3rd decimal place or better. Thus, a molecular formula can be unambiguously assigned to a compound. This makes high resolution mass spectrometry ideally suitable for identification of compounds and untargeted analyses. The two techniques are frequently used for this purpose: orbitrap and time-of-flight (TOF) mass spectrometry. Orbitrap mass spectrometers may have a higher resolution than TOF systems. However, the latter are clearly less sensitive to interferences caused by complex matrices and have a higher linear range. For both metabolomics and identification of drugs typically highly complex matrices have to be analysed and thus a QTOF is the system of choice. Usually, the high resolution analysers are often combined with a quadrupole and a collision cell to allow the selection and fragmentation of compounds. For fragmentation of molecules typically collision cells are used where the analyte ion may collide with an inert gas like argon or nitrogen and thereby break into fragments (CID, collision induced dissociation). This may provide information about the molecular structure of the analyte. Recently, electron activated dissociation (EAD) has been introduced as a powerful alternative technique for fragmentation. For EAD electrons of a selected kinetic energy are used for fragmentation. This creates a higher number of more informative fragments than CID, allowing robust and reliable identification of compounds. Taken together, the combination of liquid chromatography with EAD fragmentation and TOF mass spectrometry is ideally suitable for metabolomics and identification of compounds in complex matrices. This will allow in depth analysis of metabolic responses of plants to stress conditions, enhance identification of novel plant metabolites and help to elucidate so far ill-defined metabolic pathways.

• DFG Programme: Major Instrumentation Initiatives
• Major Instrumentation: ZENOTOF 7600 LC-MS/MS
• Applicant Institution: Hochschule Anhalt
• Leader: Professor Dr. Wilfried Rozhon
• Co-Investigator: Professor Dr. Tim Reuter