MIXTURE ANALYSIS TECHNIQUES USING MS/MS AND COMPUTER AUTOMATION
Abstract
Mixture analysis techniques using MS/MS have been refined by extensive automation of a reversed geometry (magnet preceding electric sector) mass spectrometer. A complete data system based on the HP RTE II operating system is described which enables unique experiments to be quickly configured. Routine MS/MS is fully supported including ensemble averaging, time profiling, and data manipulation and storage. Applications include the detection of 1-methyladenine in the pyrolyzate of salmon sperm DNA, which is the first report of this modified base in DNA. The possibility of pyrolysis induced artifacts is discussed in relation to enzymatic studies. Automated single reaction monitoring is used to assay intact plant tissue for 4 (beta)-hydroxywithanolide. Semi-quantitative results indicate the relative abundance of this anti-cancer agent in various parts of the plant. Leaves are found to contain the highest concentration. The versatility of MS/MS is further demonstrated by investigation of the gas phase butyl ion structure via double CID. A collision cell in the first field free region of the mass spectrometer is used to produce butyl cations. These collisionally created ions are subsequently analyzed after CID in the second field free region. The differentiation of tertiary and secondary butyl structures is indicated by a series of consistent results which complements data from other labs. One result indicates isomerization of isobutyl ions to the tertiary form. Alternative interpretations of the data including consideration of internal energy effects are also discussed. Laser desorption is used to produce silver ions which form gas phase asymmetric dimer adducts with alcohols. MS/MS of those adduct ions forms the basis for a procedure to order the relative silver ion affinities of six selected alcohols. Data acquisition is synchronized to the pulsed laser desorption profile. The hardware and software for this and all other experiments performed on the MIKES is fully described. Source codes for the Purdue Mass Spec Data System are included in the appendix.
Degree
Ph.D.
Subject Area
Analytical chemistry
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