John E. Carr

Publication Date

2007

Document Type

Dissertation/Thesis

First Advisor

Carnahan, Jon W.

Degree Name

Ph.D. (Doctor of Philosophy)

Legacy Department

Department of Chemistry and Biochemistry

LCSH

High performance liquid chromatography; Inductively coupled plasma atomic emission spectrometry; Inductively coupled plasma mass spectrometry

Abstract

Inductively coupled plasmas (ICPs) efficiently excite and ionize metals and semi-metals allowing for their detection by atomic emission spectroscopy (AES) or mass spectrometry (MS). Nonmetal analytes are more difficult to detect due to their higher excitation and ionization energies. The sensitive detection of nonmetal analytes is becoming increasingly important in the pharmaceutical industry as new drug compounds and impurities containing nonmetals are being developed. These compounds are typically detected after they are separated by high performance liquid chromatography (HPLC). The research presented in this dissertation investigates the application of ultrasonic nebulization and membrane desolvation (USN-MD) with ICP-MS and ICP-AES as detectors for nonmetal analytes speciated by HPLC. A study identified which HPLC mobile phases and buffers lead to sensitive determinations for a phosphorus-containing analyte with ICP-AES and ICP-MS detection. For ICP-AES detection, neither large signal enhancements nor degradations were observed for the buffers and mobile phase combinations tested. It was determined that gradient elution could be performed with USN-MD-ICP-AES detection. For ICP-MS detection, effects of these buffers were more significant. A large decrease in sensitivity was noted when the mobile phase included organic solvents. Isocratic elution conditions are suggested when USN-MD-ICP-MS detection is utilized. The addition of supplemental gases to the nebulizer gas flow of an ICP-MS was also investigated. For oxygen addition, signal degradation was noted for sulfur-, phosphorus-, and chlorine-containing analytes. It was determined that 6 % oxygen in the nebulizer gas flow yielded efficient removal of carbon while not appreciably increasing detection limits. With nitrogen addition, a large increase in the background signal was found for phosphorus determinations. A decrease in sensitivity was found when determining sulfur. Helium addition did not produce significant deviations from standard argon ICP behavior, indicating that it is not being significantly ionized. A final study utilized ICP-MS as a detector for the separation of several model analyte systems. It was found that significant band broadening occurred for several volatile analytes, reducing sensitivity and negatively affecting chromatographic figures of merit. However, nonvolatile analytes yielded sensitive determinations.

Comments

Includes bibliographical references (pages [215]-221).

Extent

xvi, 221 pages (some color pages)

Language

eng

Publisher

Northern Illinois University

Rights Statement

In Copyright

Rights Statement 2

NIU theses are protected by copyright. They may be viewed from Huskie Commons for any purpose, but reproduction or distribution in any format is prohibited without the written permission of the authors.

Media Type

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