Inductively coupled plasma torch with adjustable sample injector

An induction plasma generating system comprising:

• a tubular torch member having an axis and being formed of electrically insulating heat-resistant material;
• means for passing plasma-forming gas through the torch member in a forward direction;
• a helical induction coil with an axis, a forward edge and a rearward edge, disposed outside of and substantially concentrically with the torch member so as to energize the gas as a plasma discharge in a plasma region in the torch member;
• injection means for injecting a sample substance into the gas in the torch member, comprising a ceramic pipe having a forward orifice end with an orifice therein mounted coaxially within the torch member and means for passing the sample substance in fluid form forwardly through the orifice;
• a torch assembly including the torch member and the ceramic pipe, the ceramic pipe being affixed with respect to the torch member;
• adjusting means for adjusting the position of the torch assembly in an axial direction with respect to the induction coil while the gas is being energized, including means for varying the position of the orifice end between a first location and a second location, the first location being proximate a first plane that is oriented perpendicularly to the axis of the induction coil in contact with the forward edge of the induction coil, and the second location being proximate a second plane that is oriented perpendicularly to the axis of the induction coil in contact with the rearward edge of the coil;
• means for initiating the plasma discharge while the orifice end is positioned at the first location, the adjusting means further including means for relocating the orifice end from the first location to the second location after the plasma discharge is initiated.

A plasma generating method for use with an induction plasma generating system having a tubular torch member formed of electrically insulating heat resistant material, a helical induction coil disposed outside of and substantially concentrically with the torch member, and injection means for injecting a sample substance into the gas in the torch member, the induction coil having an axis, a forward edge and a rearward edge, the method comprising:

• positioning the injection means at a first location proximate a first plane that is oriented perpendicularly to the axis of the induction coil in contact with the forward edge of the induction coil;
• initiating a flow of plasma-forming gas through the torch member in a forward direction;
• energizing the flowing gas as a plasma discharge in a plasma region in the torch member by means of the induction coil;
• and
• while the flowing gas is being energized, adjusting the position of the injection means in an axial direction with respect to the induction coil from the first location to a second location proximate a second plane that is oriented perpendicularly to the axis of the induction coil in contact with the rearward edge of the coil.