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.