TANDEM MASS SPECTROMETRY: APPLICATIONS AND NEW INSTRUMENTATION
Abstract
Applications of tandem mass spectrometry (MS/MS) in complex mixture analysis and the development of a new MS/MS instrument are described. The MS/MS methodology is applied to the analysis of coal liquids and diesel particulates. Individual components are identified by daughter scans, while parent and neutral loss scans are used to screen the mixture for selected types of compounds. The selective ionization methods of negative chemical ionization and ammonia chemical ionization are employed to increase specificity in these analyses. High and low energy MS/MS data are compared for a group of isomeric pairs of methyl aza and amino polynuclear aromatic compounds. Quite different spectra are observed in the two energy regimes, however, in both regimes the isomers are distinguishable. A library of low energy MS/MS spectra is developed on a triple quadrupole mass spectrometer and is used for the identification of individual components in a diesel particulate sample. Chemical ionization mass spectrometry is used for the quantitation of methylated nucleosides formed from in vitro and in vivo DNA alkylations. The potential for tandom mass spectrometry to decrease detection limits in these determinations is shown. A new hybrid mass spectrometer is constructed for MS/MS studies and its performance evaluated. The new instrument, of BEQQ configuration, combines a double focussing mass spectrometer with a quadrupole collision cell and a quadrupole mass analyzer. The instrument features four different reaction regions and is capable of high resolution MS/MS, high and low energy MS/MS, and consecutive collision experiments. New scan types are also possible. Studies on a variety of systems establish that the BEQQ performs well for low energy MS/MS. High resolution and high mass MS/MS capabilities are also demonstrated. Early applications, including parent scans and consecutive collision experiments, are described. In addition, an improved arrangement for angle-resolved mass spectrometry, which utilizes the BE section of the hybrid instrument, is described.
Degree
Ph.D.
Subject Area
Analytical chemistry
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