Trace detection in conducting solids using laser-induced fluorescence in a cathodic sputtering cell

Abstract

A cathodic sputtering atom reservoir designed for atomic absorption spectrometry of conducting solid samples is examined as a potential sampling device for trace and ultra-trace detection using laser-induced fluorescence (LIF) spectrometry. The analytical results are promising, with sub-µg g^–1 sensitivity for the model analyte (Fe) in brass samples, and with reasonable precision and accuracy (±15%) for the pulsed laser system used, but with far less sensitivity than might be predicted. Noise studies clearly indicate that laser-induced background fluorescence is the principal limiting noise source. Fundamental material transport studies indicate that diffusional loss of atomic number density to the walls is of much less importance than the background fluorescence in determining the sensitivity of the system. Extrapolations based on cell–experiment design to maximize number density and minimize background emission and fluorescence promise ng g_–1 sensitivities for future implementations.