Date of Award
Doctor of Philosophy
Robert S. Houk
The focus of this dissertation is the development of techniques with which to enhance the existing abilities of inductively coupled plasma mass spectrometry (ICP-MS). ICP-MS is a powerful technique for trace metal analysis in samples of many types, but like any technique has certain strengths and weakness. Attempts are made to improve upon those strengths and to overcome certain weaknesses.;One standout figure of merit for ICP-MS is limit of detection. With today's advances in instrumental hardware the limit of detection is often limited by the purity of the blank. While the limit of detection itself is not evaluated, by improving blank cleanliness it is theoretically possible to get improvements in this area. A metal-free, low-pressure, electrochemically modulated liquid chromatography (EMLC) column was designed and evaluated specifically for use on-line with ICP-MS. The EMLC column reduces levels of trace elements in blank solutions just before the blank is introduced into the nebulizer. The stationary phase is reticulated vitreous carbon (RVC), and the reference and counter electrodes are positioned upstream from the column to minimize contamination. Many metal ions can be removed at a single applied potential of ∼-0.75 V (vs SHE).;Analysis of samples with high matrix concentrations is a relative area of weakness for ICP-MS. Solution samples with matrix concentrations above ∼0.1% generally present difficulties due to cone clogging and matrix effects. Flow injection (FI) is coupled to ICP-MS to reduce clogging from samples such as 1% sodium salts and seawater. Surprisingly, matrix effects are also less severe during flow injection, at least for some matrix elements on the particular instrument used. Sodium chloride at 1% Na and undiluted seawater cause only 2 to 29% losses of signal for typical analyte elements. A heavy matrix element (Bi) at 0.1% also induces only ∼14% loss of analyte signal. However, barium causes about the same matrix effect as usual. Also, matrix effects during FI are of the usual magnitude when a metal shield is inserted between the load coil and torch, which is the most common mode of operation for the particular ICP-MS device used.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Cory Thomas Gross
Gross, Cory Thomas, "Developments in ICP-MS: electrochemically modulated liquid chromatography for the clean-up of ICP-MS blanks and reduction of matrix effects by flow injection ICP-MS" (2008). Retrospective Theses and Dissertations. 15810.