Modified plasma torch design for introducing sample air into inductively

Abstract

A plasma torch for reliable analysis of airborne particulate matter permits real-time monitoring of airborne metal pollutants in flue gases from furnaces and incinerators. The torch injects sample air into argon plasma and has an outer tube to confine plasma gas for generating a plasma fireball. An intermediate tube has an outwardly flared portion concentrically disposed within the outer tube to form an outer annulus for feeding plasma gas to the fireball. The intermediate tube also has an injector sheath tube joined at its base to the base of the flared portion and concentrically disposed within the flared portion. The injector sheath tube is parallel to the outer tube. An inner capillary injector tube injects sample air into the plasma fireball. The inner capillary injector tube is concentrically disposed within the injector sheath tube to form an inner annulus that directs annular flow of auxiliary gas to alter the surface of the central region of the plasma fireball and channels the sample air to inject it through the surface and into the plasma fireball. The annular flow of auxiliary gas assures injection of the sample air at velocities which preserve residence time of the sample air to effect efficient vaporization and excitation of the metals.