Date of Award
Doctor of Philosophy
R. S. Houk
Noise power spectra of the [superscript]85Rb[superscript]+ signal and the [superscript]93Nb[superscript]+ signal from an inductively coupled plasma-mass spectrometer were compared to the noise power spectrum of Sr II emission from the plasma. Discrete frequency noise in the emission at the mass spectrometer sampling orifice was found to be nearly identical to that in the mass spectrometer signal. However, discrete frequency noise in emission from the plasma alone differed substantially in frequency from that in the mass spectrometer signal. The dependence of noise frequencies on plasma operating conditions was generally the same for the mass spectrometric measurements and both emission measurements. These results indicate that the plasma was the source of discrete frequency noise in the mass spectrometric signal. The major source of signal instability in this particular ICP-mass spectrometer was found to be 1/f noise;A new, home-made ICP-mass spectrometer was used to study the influence of Na, K, and U on ion signals from Y, Co, and As. In general, analyte signals were suppressed in the presence of excess matrix element. The extent of suppression was greatest for the element with high ionization energy (As) and least for the element with the smallest ionization energy (Y). These trends in the interference effect could be altered by applying a positive voltage to the first element of the ion optics. When the skimmer orifice diameter was made smaller than the sampling orifice diameter, analyte signal suppression was uniform and more extensive. Under these conditions, the heavy matrix element (U) induced more suppression than did the light matrix element (Na);Degrees of ionization for As and Sb in an inductively coupled plasma were measured using mass spectrometry, and electron density (n[subscript] e) in the plasma just upstream of the mass spectrometer sampling orifice was measured from Stark broadening of the H I 486.13 nm emission line. These data were used to calculate ionization temperature (T[subscript] ion) for Sb and As over the range of plasma conditions studied. Variations of Sb T[subscript] ion with plasma conditions were consistent with those expected of the ICP itself, however, such was not always the case for As T[subscript] ion. It was found that T[subscript] ion for Sb was generally higher than that of As, indicating that the ionization kinetics of Sb may differ from those of As. ftn*The work was performed at the Ames Laboratory under contract no. W-7405-ENG-82 with the U.S. Department of Energy. The United States government has assigned DOE report no. IS-T-1413 to this dissertation.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Jeffrey Scott Crain
Crain, Jeffrey Scott, "Fundamental characteristics and applications of an inductively coupled plasma as an ion source for mass spectrometry " (1989). Retrospective Theses and Dissertations. 9031.