New development in ICP spectrometry: low flow torch for axial viewing ICP-AES & studies in semiconductor analysis by ICP-MS

Hasan, Towhid
Major Professor
R. S. Houk
Committee Member
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A low argon flow torch has been developed for axially viewed ICP-AES. Outer argon flow has been drastically reduced (less than 7 L min-1 ) by cooling the torch wall with air passing through a cooling jacket added to the outside of a Fassel torch. The plasma is viewed axially through a cooled cone interface centered on the axial channel. Although detection limits (DL) for lines at ~200 nm are poorer by about a factor of two, those for lines at ~400 nm are actually much better than values typically seen for the same lines by axial viewing of a conventional, high-flow ICP.;Silicon measurement at m/z 28, 29 and 30 by ICP-MS is complicated by the spectral interferences caused by organic molecular ions, nitrogen and nitrogen oxides. A method has been developed to measure silicon in organic solvents by reducing polyatomic interferences at m/z 28 to 30 using cryogenic desolvation for removal of organic solvent from the wet droplets in aerosol, and by adding krypton or xenon to the sample gas flow of plasma. Isotope ratios can be measured by medium resolution (R = 4000) ICP-MS by direct nebulization of organic solvents. To avoid deposition on the interface cone, the flow of oxygen in the spray chamber is adjusted to titrate carbon in the plasma. Despite the sharply pointed peaks at R = 4000, ratio precision of +/-0.1% RSD can be obtained using approximately 1 mug of silicon.;Electrochemically modulated liquid chromatography (EMLC) column has been adapted online with ICP-MS to clean up blanks to reduce background signals. Metal ions can be retained from the flow of blanks in the micrometer size glassy carbon particle packing with appropriate negative potential. A Ag/AgCl (satd. NaCl) reference electrode in dilute nitric acid supporting electrolyte was used for electrochemical cell combination. Several metal ions have found to be retained with >99% extraction efficiency from the blank solution. Cleaning of the column can be done easily by stripping the deposited metal with a high positive potential.