Degree Type

Dissertation

Date of Award

1991

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

R. S. Houk

Abstract

A simple variation in sample preparation and introduction allows the measurement of chlorine isotope ratios by inductively coupled plasma mass spectrometry (ICP-MS). Dissolution of the sample in D[subscript]2O rather than H[subscript]2O attenuates the major polyatomic ion [superscript]36ArH[superscript]+ and frees m/z = 37 for determination of [superscript]37Cl[superscript]+. The isotope ratio [superscript]35Cl/[superscript]37Cl in a 50 mg L[superscript]-1 solution of Cl as LiCl is determined with a relative standard deviation (RSD) of 0.21%. Sample memory is low as the [superscript]35Cl[superscript]+ signal decays to less than 1% of its original value after ~2 min of cleanout with D[subscript]2O. The detection limit for chlorine using this procedure is approximately 20 [mu]g L[superscript]-1;A method for the determination of boron in a variety of biological samples is described. Sample material is fused with Na[subscript]2CO[subscript]3 and boron is separated from matrix components by using Amberlite IRA-743 boron selective ion-exchange resin. Boron is eluted with 1% HNO[subscript]3 and samples are introduced to an ICP-mass spectrometer with a direct injection nebulizer (DIN). This nebulizer provides a fast sample cleanout of ~15 seconds. The [superscript]10B/[superscript]11B ratio is determined with an RSD of 0.4% to 1.5%, and the detection limit for boron is approximately 1 ng g[superscript]-1 in these samples;Xenon is added at 10 or 37 mL min[superscript]-1 to the aerosol gas flow of an argon ICP-mass spectrometer. Addition of Xe substantially reduces polyatomic ions such as N[subscript]2[superscript]+, HN[subscript]2[superscript]+, NO[superscript]+, ArH[superscript]+, ClO[superscript]+, ArC[superscript]+, ClOH[superscript]+, ArN[superscript]+, and ArO[superscript]+ and facilitates the measurement of Si, K, V, Cr, and Fe. Isotope ratios are determined with RSDs from 0.6% to 1.6%. Detection limits for the above elements range from 0.3 [mu]g L[superscript]-1 to 2 [mu]g L[superscript]-1;Addition of Xe to the ICP does not change the electron density (n[subscript] e) or the excitation energy (T[subscript] exc) of the gas flowing into the sampling orifice. However, ionization temperature (T[subscript] ion) drops by approximately 400 K when Xe is added. The suppression of analyte signal by Xe can be mimicked. However, the Cs matrix does not induce a corresponding drop in T[subscript] ion by addition of an appropriate amount of Cs matrix to an all-Ar plasma. These experiments indicate that addition of Xe is largely a matrix effect, and the drop in T[subscript] ion may account for the preferential loss of interferent ions versus analyte ions.

DOI

https://doi.org/10.31274/rtd-180813-11332

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Fred Grover Smith

Language

en

Proquest ID

AAI9202389

File Format

application/pdf

File Size

123 pages

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