Further development, optimization and characterization of in-torch vaporization-inductively coupled plasma (ITV-ICP) spectrometry

An in-torch vaporization (ITV) sample introduction has been developed as a means of addressing the shortcomings of traditionally used nebulization-based sample introduction systems for inductively coupled plasma (ICP) spectrometry. The objective of this project was to further develop ITV for ICP spectrometry with a focus on improving elemental detection limits.; An ITV system with a Re cup sample holder was optimized with a radially (side-on) viewed ICP atomic emission spectrometry (AES) system. The utility of Re cups allowed direct analysis of solid samples (e.g., paint chips) by ITV-ICP-AES. The next generation of ITV systems capitalized on the reportedly better sensitivity of axially (end-on) viewed ICP-AES systems. The improved sensitivity obtained by optimizing a horizontally operated ITV system and an axially viewed ICP-AES, allowed nanogram amounts of samples (e.g., a single cell or a grain of pollen) to be analyzed and, for the first time, attogram detection limits by ICP-AES were achieved as a result of this work. In addition, Re coils, as alternative ITV sample holders, were used for preconcentration by electrodeposition. The utility of an electrodeposition step not only improved analyte detection limits (30--50 times), but also allowed the removal of concomitant matrix from the sought-for analyte.; The next part of the project focused on spectral features of ITV-ICP mass spectrometry (MS) and showed that, compared to the mass spectra obtained by solution nebulization, ITV-ICP-MS spectra are simpler mostly due to the removal of water as the major source of oxygen in the plasma. This was later used to show the capabilities of ITV as an alternative solution to the problem of spectral interferences in ICP-MS. In addition, the micro-sampling capability of ITV combined with the sensitivity of ICP-MS facilitated a unique application, namely the determination of rare-earth (e.g., Eu) tags in immunoassays.; Further, the capability of ITV in selectively vaporizing sample constituents with different volatilities allowed interference-free determinations by separating the analyte signal, in time, from that of the concomitant matrix.; Finally, the design of the ITV vaporization chamber was studied based on principles of fluid dynamics. For the first time, computational fluid dynamics (CFD) was used to simulate the gas flow in an ITV chamber. Based on the simulation results, the ITV vaporization chamber was redesigned and tested with elements that previously had shown picogram detection limits by ITV-ICP-AES ( i.e., Zn, Pb, and Cd). The redesigned chamber improved the detection limits even further and well into the femtogram range for Zn, Pb, and Cd. At the end of this project, the overall improvements in detection limits for all elements tested were, in some cases, two orders of magnitude or more compared to those reported prior to this work.