Date of Award
Doctor of Philosophy
Robert Sam Houk
Chapter 1 describes a new method for surface analysis of steel by controlled dissolution with aqueous acid mixtures at room temperature. The dissolved elements are diluted and determined by a magnetic sector ICP-MS device. Analyte concentrations in the solid are determined from the ratio of "(analyte ion signal)/Fe+ signal". The measured concentrations for elements like Mn, Al and W in steel agree well with the certified values, whereas those for problem elements as Nb and Ta are lower than the certified values. Laser ablation ICP-MS and scanning electron microscopy (SEM) measurements show these elements to be associated together in the solid in refractory grains that are not dissolved to the same extent as the Fe matrix.;Chapter 2 is a continuation of a previous project. The behavior of bacteria (B. subtilis) in the ICP is investigated by monitoring the time-resolved U+ signal since U is incorporated intrinsically in bacteria. Sonication of bacteria for a short period of time (5 minutes) increases the U+ response compared to the untreated sample, while further increases in sonication time do not generate more U + signal. The chromatographic results for 10 ppb U standard, partially lysed and fully lysed bacteria samples show that the U-bound species is released by sonication and small in size. The positive U+ spike effect from bacterial sample shows that bacteria behave like large particles in the ICP. The fact that desolvation of the bacteria aerosol does not eliminate the spikes suggests that they are not due to solvation. The interaction of PEEK tubing with intact bacteria is also investigated by flow injection analysis (FIA).;In Chapter 3, the formation of M(NO3)x- ions are studied by electrospray ionization (ESI) in negative mode and their collision-induced reactions are monitored in a triple quadrupole (QoQ) tandem mass spectrometer (MS). The M(NO3)x -ions dissociate into NO3- and neutral metal nitrate molecules for Group 1 and 2 elements, while transition elements and Group 13 elements fragment into oxo products and also undergo internal electron transfer. The product ions from Fe(NO3) 4- ions have low formation thresholds of only 0.5 to 2 eV.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu
Li, Fumin, "Inorganic and biological applications of inductively coupled plasma mass spectrometry and electrospray mass spectrometry " (2004). Retrospective Theses and Dissertations. 798.