Semester

Summer

Date of Graduation

2002

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Chemistry

Committee Chair

Fred L. King.

Abstract

Plasma sources for optical spectroscopy and mass spectrometry have provided scientists unprecedented knowledge about the fundamental properties and behavior of matter. As informative and useful as these methods are; however, there is still considerable room for improvement. The accuracy and precision of quantitative analyses by mass spectrometry and optical emission spectroscopy are often dependent on the presence of interferences. Interferences are defined as a measured signal response to a species at the spectral position of interest for the analyte that is not caused by the analyte. Because the presence of spectral interferences can deleteriously affect the integrity of reported results, methods are required to reduce, eliminate, or otherwise compensate for the interfering signals. This study focuses on two such methods for reducing spectral interferences.;The first method is to operate the glow discharge source in a transient mode in order to spatially and temporally resolve analyte and interfering signals. The second method is to employ collision-induced dissociation in a quadrupole ion trap in order to reduce molecular interferences in atomic mass spectrometry.;Optical and mass spectrometric studies are described in which the spatio-temporal evolution of the pulsed glow discharge is elucidated. The sequences of events following voltage termination of a 5-millisecond pulse are studied in detail, especially concerning reactions leading to the generation of analyte ions and excited states. The addition of nitrogen as a diagnostic tool is serendipitously found to enhance the temporal characteristics that separate the plasma gas emissions and ions from the sputtered analyte emissions and ions. This could lead to future applications for time-gated detection methods in optical and mass spectrometric analyses that minimize interferences due to plasma species.;Collision-induced dissociation of strongly bound molecular interferences in a quadrupole ion trap is examined as a potential means for the removal of these interferences. Methods for determining the dissociation rates and factors affecting the dissociation rates and efficiencies are also investigated, along with a method for determining the bond dissociation energy of diatomic ions. Such collision-induced dissociation in the quadrupole ion trap is also shown to be possible while simultaneously trapping bare metal ions at the same nominal mass. These findings could eventually lead to the ability to acquire purely elemental mass spectra with minimal operator intervention.

Download

Share

COinS