Date of Award
Doctor of Philosophy
R. S. Houk
A new version of the direct injection nebulizer (DIN) is used to interface liquid chromatographic (LC) separations with element - selective detection by inductively coupled plasma - mass spectrometry (ICP-MS). The advantages of using LC-DIN-ICP-MS include little dead volume, low sample and solvent consumption, excellent plasma stability when nebulizing samples containing concentrated organic solvent, excellent absolute detection limits, excellent precision, superior chromatographic resolution, and reduced memory effects from memory-prone elements (e.g., Hg);Various compounds containing arsenic (AsO[subscript]2[superscript]-, HAsO[subscript]4[superscript]2-, CH[subscript]3AsO[subscript]3[superscript]2- and (CH[subscript]3)[subscript]2AsO[subscript]2[superscript]-), tin (CH[subscript]3Sn[superscript]3+, (CH[subscript]3)[subscript]2Sn[superscript]2+, (C[subscript]2H[subscript]5)[subscript]2Sn[superscript]2+ and (CH[subscript]3)[subscript]3Sn[superscript]+), mercury (Hg[superscript]+2, CH[subscript]3Hg[superscript]+, C[subscript]2H[subscript]5Hg[superscript]+ and C[subscript]6H[subscript]5Hg[superscript]+) and lead (Pb[superscript]+2, (CH[subscript]3)[subscript]3Pb[superscript]+ and (C[subscript]2H[subscript]5)[subscript]3Pb[superscript]+) are separated by reversed-phase ion-pairing LC. Selenium species (SeO[subscript]3[superscript]2- and SeO[subscript]4[superscript]2-) are separated by ion chromatography (IC). Several metalloproteins containing Na, Fe, Cu, Zn, Cd, Ba, and Pb are separated by size-exclusion chromatography (SEC). Some of these compounds are separated and measured in biological and environmental samples such as human urine and human serum. Detection limits are ≈3, 0.7, 1, 0.5, 5, 0.5, 15, 7, and 0.2 pg for Fe, Cu, Zn, As, Se, Cd, Sn, Hg, and Pb, respectively. Microbore (1-2 mm i.d.) packed columns are employed because the liquid flow rates used (30-100 [mu]L min[superscript]-1) are compatible with the DIN;Aerosol droplet sizes and velocities from a DIN are measured with radial and axial spatial resolution by phase doppler particle analysis (PDPA). The droplets on the central axis of the spray become finer and their size becomes more uniform when ≈20% methanol is added to the usual aqueous solvent. This could explain why the analyte signal is a maximum at this solvent composition when the DIN is used for ICP-MS. Mean droplet velocities are 12 to 22 m s[superscript]-1 with standard deviations of ±4 to ±7 m s[superscript]-1. The outer fringes of the aerosol plume tend to be enriched in large droplets. The Sauter mean diameter (D[subscript]3,2) and velocity of the droplets also vary substantially with axial position in the aerosol plume. These findings are valuable for improving the analytical performance of the DIN.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Sam Chiu-Kin Shum
Shum, Sam Chiu-Kin, "Measurement of elemental speciation by liquid chromatography: inductively coupled plasma mass spectrometry (LC-ICP-MS) with the direct injection nebulizer (DIN) " (1993). Retrospective Theses and Dissertations. 10273.