Advances in direct solution introduction for inductively coupled plasma mass spectrometry and their applications to ultratrace elemental analyses.

摘要

The main objective of this research is to explore new, innovative methods for the direct introduction of microliter volumes of test samples in inductively coupled plasma mass spectrometry (ICPMS) and ICP atomic emission spectrometry (ICPAES). The benefits and drawbacks of direct injection nebulization into ICPs are also investigated as they apply to the analysis of several diverse sample types. The micronebulizers used in these studies include a commercially-available direct injection high efficiency nebulizer (DIHEN) and large bore-DIHEN (LB-DIHEN). A relatively simple, inexpensive laboratory version of the DIHEN, the demountable-DIHEN (d-DIHEN), is also developed as part of this research. The d-DIHEN features a tunable solution capillary which provides improved analytical performance at low (<20 μL/min) solution uptake rates. Point-measurement aerosol diagnostic techniques, such as two-dimensional phase-Doppler particle analysis (2D-PDPA), are used to better understand aerosol generation processes involved for direct injection nebulizers. Alternative approaches to typical direct injection nebulizers are also explored. A novel short torch is developed as part of this research to allow for any micro- and conventional pneumatic nebulizer to be used as a direct injection nebulizer. Collectively, these new methods offer several benefits over conventional nebulizer-spray chamber, including: reduced memory effects, 100% analyte transport efficiency, low sample consumption (∼1 to 100 μL/min), better precision, similar to or enhanced relative detection limits (ng/L to pg/L), and improved relative sensitivity (MHz to GHz/ppm). Finally, the developed direct injection techniques are applied to the analyses of biological, environmental, industrial, medical, nuclear, and pharmaceutical samples using a wide range of techniques and spectrometric systems, including capillary electrophoresis, quadrupole ICPMS, double-focusing ICPMS, collision cell ICPMS, and axially- and radially-viewed ICPAES.