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Laser-Excited Atomic Fluorescence of Eu, Y, and Tm in a Miniature Glow Discharge Atom Reservoir

A miniature glow discharge (GD) is evaluated as an atom reservoir for laser-excited atomic fluorescence spectrometric measurements of Eu, Y, and Tm. Nanoliter-sized aqueous samples are deposited and dried on the Ni cathode and atomized upon ignition of the GD. The atom population is probed by a copper vapor laser pumped dye laser, and direct-line fluorescence is detected. The optimum chamber pressures and operating currents are 1 Torr and 10 mA for Eu, 2 Torr and 10 mA for Y, and 3 Torr and 40 mA for Tm. The fluorescence temporal profiles are found to consist of short (∼20-ms duration) transient spikes, followed by long tails which last more than 60 s as a result of sample redeposition on the cathode surface. The limits of detection (3a) are 2 fg, 1.2 pg, and 0.08 fg for Eu, Y, and Tm, respectively, with the use of signal area integration over a 6-s duration. Theoretically simulated signals for a particular sample mass, considering the geometry of the GD atomizer, were found to fall within one order of magnitude of those obtained by experiment.