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.

Laser-Induced Fluorescence of Atoms in a Power-Modulated Inductively Coupled Plasma for Trace Detection and Diagnostic Study

Laser-induced fluorescence of iron atoms during the plasma-off cycle of a power-modulated inductively coupled plasma has been performed. The low plasma background emission, and absence of radio-frequency interference, 1.4 ms after complete interruption of power to the ICP, results in an excellent environment for fluorescence detection. With the use of a simple nondispersive detection system, a limit of detection of 5 µg Fe/L was achieved. The iron atom population was found to remain constant for 1.2 ms after power interruption, indicating that the chemical environment during this period is inert. A spatial profile and ICP power study were conducted as diagnostic aids for optimization of the power-modulated ICP for both fluorescence and ionization detection.

Fabrication and Utilization of a High-Power Microwave Supply for Electrodeless Discharge Lamps and other Spectrochemical Emission Sources

A study of the factors influencing the performance of a microwave-induced discharge shows that the analytical utility generally increases as the applied microwave power is increased. The fabrication of an easily used high-power system (500 W) is described; the system is used to excite electrodeless discharge lamps of relatively high-boiling species, multielement lamps, and an atmospheric-pressure flowing plasma. The system has been used to study vaporization phenomena in a cadmium electrodeless discharge lamp. The ground-state atom population, as measured by absorption, appears to be directly related to the thermal (wall) temperature.