Noise characteristics of aerosols produced by inductively coupled plasma nebulizers

Abstract

The noise characteristics of aerosols produced by inductively coupled plasma nebulizers were investigated. A laser beam was scattered by aerosol and detected by a photomultiplier tube and the noise amplitude spectrum of the scattered radiation was measured by a spectrum analyser. Discrete frequency noise in the aerosol generated by a Meinhard nebulizer or a direct injection nebulizer was primarily caused by pulsation in the liquid flow from the pump. By use of a pulse-free pump, such as a gas displacement pump or a dual piston pump for liquid chromatography, the discrete frequency noise was eliminated. The configuration of the spray chamber affected the level of white noise. A Scott-type spray chamber suppressed white noise, while a conical, straight-pass spray chamber enhanced white noise, relative to the noise seen from the primary aerosol. The noise in the aerosol from a continuous-flow ultrasonic nebulizer had a relatively high 1/f component.