Three-phase double-ARC plasma for spectrochemical analysis of biological samples

A new instrument, which uses a three-phase current to support two argon plasma arcs for sampling and excitation of solid or powder samples, is described. Each arc consists of a cylindrical brass housing, adjustable sample height holder and graphite electrodes. The sampling arc is ignited between the sample surface and the graphite electrode. Argon gas stream is introduced through the graphite tube electrode and directed to the surface of the sample electrode the argon gas transport the sample vapor to the excitation arc through plastic tubing. The excitation arc bums between graphite rod electrode and graphite disc electrode with a small orifice in its center. The excitation arc is generated between the two electrodes. A partially ionized gas formed between the two electrodes of excitation arc is forced at high velocity through the small orifice of the disc electrode. The extracted plasma from the orifice has a flame like appearance and spectroscopic observation are made in the non current carrying plasma plume. An evaluation of each parameter influencing the device performance was performed. Analytical calibration curves were obtained. Finally the present technique was applied for the analysis of some biological samples. The present method appears to have significant, low cost analytical utility for bone samples.