Abstract

Mass Spectrometry - Current Approaches and New Vistas

Mariappanadar Vairamani, Dean, SRM University

21st century started reaping the fruits of extensive research in the development of mass spectral instrumentation and new ionization techniques, carried out during the previous century. Mass spectrometers are no longer considered as instruments which require specialized skills to operate and maintain and they have become user friendly and miniaturized. Instruments with high resolution (FWHM) like, Time-of flight (>75,000), Orbitrap (2,40,000), and FT-ICR (6,00,000 to 1,00,00,000) configurations have almost replaced magnetic sector instruments for achieving high resolution measurements. Electron impact (EI) and chemical ionization (CI) techniques continue to be the ionization methods of choice for unambiguous characterization of volatile and thermally stable compounds. For the analysis of polar and nonvolatile compounds, electrospray ionization (ESI) and matrix assisted laser desorption ionization techniques have become very reliable and have increased the user base exponentially during the last decade. Different variants of ESI and related ionization techniques are now commercially available for specific and common applications. Mass spectral imaging is another area which is being explored for its routine use. Rapid evaporative ionization mass spectrometry is another technique which is being validated for its use in cancer surgery. In situ metabolic analysis of single plant cell has been achieved by capillary micro sampling and mass spectrometry. However, identification of unknown compounds remain a challenge especially using softer ionization techniques, because these techniques do not generate radical cations and hence, give limited fragment ions upon collision activation for characterization and comparison. Electron transfer dissociation and related techniques are available, though they are mainly used in protein/peptide characterization. Again, the collision induced dissociation based MS-MS libraries are very much dependent upon the instrumental conditions unlik