NOISE CHARACTERISTICS IN INDUCTIVELY COUPLED PLASMA OPTICAL-EMISSION SPECTROMETRY USING SLURRY NEBULIZATION AND DIRECT POWDER INTRODUCTION TECHNIQUES

By use of Fourier analysis, the noise sources of inductively coupled plasma optical emission spectrometry (ICP-OES) were examined for two common types of torches, a Greenfield and a Fassel type torch. Furthermore, the dominant noise types occurring by the nebulization of solutions and suspensions using a Babington (G.M.K.) nebulizer and by the direct Introduction of powders In the plasma were compared. Firstly, It was found that In contrast to a Fassel type torch a Greenfield type torch exhibits no discrete audio frequency (af) noise band In the 150–400 Hz region. The noise types, including af, white, flicker (1/f), and pumping noise were examined as a function of rf power, outer gas flow rate, observation height, and pumping rate. Upon the introduction of solid particles In the plasma, either as slurries or as a dry powder, a small but significant Increase (about 5%) of the af noise band frequency was observed. The precision for the analysis of suspensions (1.9%) was found to be somewhat lower than for solutions (1.4%), which may result from a small increase In flicker noise. © 1990, American Chemical Society. All rights reserved.