Recent advances in analytical spectrometric instrumentation. I. Applications of radioluminescence in spectrochemical sensing. II. Investigations of an inductively coupled plasma on-axis time-of-flight mass spectrometer for elemental analysis.

摘要

Two of the current motivating forces in analytical chemistry are (1) the desire for miniaturized instrumentation and (2) the need to analyze lower concentrations and sample masses (often at or below the part per trillion and femtogram levels). Smaller instruments will reduce costs and improve portability. Higher sensitivity makes possible the development of purer materials and more complete characterization of chemical systems. This document details studies aimed toward the solution of both of these goals.; Radioluminescence (RL) is the generation of photons by a light-producing medium after absorbing energy from radioactive decay particles. RL light sources offer flexible temporal and spectral characteristics, low cost, compact size, and high stability for remote and on-line sensing applications. Projects explored the development of radioluminescence as an alternative to conventional light sources used for spectrochemical measurements. A relatively low activity RL sources was used as an ultraviolet absorption detector for on-line flow-injection analysis. A second study involved the design of a temperature sensor based on the emission characteristics of the common phosphor ZnS:Cu.; Inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS) is a powerful technique for ultratrace elemental analysis. Strengths of ICP-TOFMS include the ability to measure most of the elements in the periodic table with excellent limits of detection, broad dynamic range, few spectral interferences, and the capability to analyze gases, liquids and solids. Research involving TOFMS can be broadly divided into two categories: transient analysis and instrumental development. Coupled with separation techniques such as gas chromatography and capillary electrophoresis, ICP-TOFMS provides excellent sensitivity while generating information about the chemical form of elements (speciation). Three studies focused on the utilization of single-shot laser ablation measurements for the direct, spatially resolved investigation of solid samples. To address the remaining performance limitations of ICP-TOFMS, the system was equipped with an ion guide collision cell to enhance spectral resolution while simultaneously reducing isobaric interferences.