Recent results have shown the potential for the direct and near real-time determination of metals in aerosols (a solid or liquid particle in a gas, e.g., an air or atmospheric sample) using a single-stage impactor connected to an electrothermal atomization atomic absorption spectrometer. The basic principle involves the drawing of an aerosol by vacuum through a jet, with the output stream directed against the electrothermal atomizer surface (impaction plate surface) opposite the injection port. The impaction plate deflects the flow rate to form an abrupt bend in the streamline, and particles in the aerosol with sufficient inertia are unable to follow the streamline and collide or impact with the electrothermal atomizer surface. The solid sample is then determined for metal content by conventional electrothermal atomization atomic absorption spectrometry. Detection limits were in the low ng/m<sup>3</sup>, the system was capable of detecting approximately 60 different metals on a sequential basis, moving mechanical parts were minimal, and the system was shown to directly determine mercury, cadmium, copper, and lead in the laboratory atmosphere.
Joseph Sneddon, "Collection Efficiency of an Impaction-Electrothermal Atomization Atomic Absorption Spectrometric System for the Direct and Near-Real-Time Determination of Metals in Aerosols: Some Preliminary Results," Appl. Spectrosc. 43, 1100-1102 (1989)