Sample introduction and solvent effects in an argon and helium microwave induced plasma

Atomic emission spectrometry (AES) with a plasma has proven to be an important method for the analysis of metallic and nonmetallic species in a variety of matrices. Not only is atomic spectrometry useful for accurate and sensitive quantitative analysis, but it can be used as a means of unambiguous qualitative determinations. The most common matrix for AES samples is liquid. Whether aqueous or organic in nature, the majority of samples are dissolved in some sort of solvent. Unfortunately, for most modes of sample introduction, a large portion of the solvent is simultaneously introduced to the plasma discharge along with the analyte species. The plasma is thus required not only to sufficiently excite the analyte, but also to desolvate and vaporize the solvent species. These processes tend to diminish the available energy of the plasma that is to be directed toward the analyte. The nature of the energy loss due to solvent loading is not well understood and is the topic of debate for different systems. It is the focus of this dissertation to determine the effect of solvent loading on the Highly Efficient Microwave Induced Plasma (HEMIP). The magnitude of solvent loading for Ar and He discharges using different sample introduction systems is determined. The solvent load is shown to have two separate constituents: aerosol and vapor. Each of these are shown to affect the plasma in different ways. Two different sample introduction systems are evaluated for their respective solvent loadings: a cooled pneumatic nebulizer / double pass spray chamber and an ultrasonic nebulization system. These systems are compared under their normal operating conditions and for the two plasma support gases. High solvent loads are shown to destabilize both the Ar and He microwave plasmas, decrease analytical sensitivity, and attenuate the energy of the plasma discharge. The conditions under which solvent loading is minimized do not have a significant effect on the operational characteristics of the sample introduction systems, but provide the optimal analytical sensitivity and limits of detection for the HEMIP.

Name thesis:degree_name

Ph. D.

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Chemistry

Department dc:contributor.department

Chemistry

Grantor dc:publisher

Virginia Tech

Year dc:date.issued

1992

Author dc:creator

• McCleary, Keith Alan

Chair dc:contributor.committeechair

• Long, Gary L.

Committee members dc:contributor.committeemember

• Anderson, Mark R.
• Schick, G. Alan
• Merola, Joseph S.
• Sanzone, George

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en

Dc Identifier Other

etd-12222005-090629

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/40444