US Patent 7554660 Plasma spectroscopy system with a gas supply

A spectroscopy system for spectro-chemical analysis of a sample includes a plasma torch (50) for generating a microwave induced plasma (90) as a spectroscopic source. The plasma forming gas is nitrogen which can contain an oxygen impurity. Thus the system includes a nitrogen generator (70) which is preferably supplied with compressed atmospheric air from a compressor (75) for oxygen to be removed from the air by adsorption. The invention allows the use of an on-site nitrogen gas generator and thus gives cost savings because the need to obtain supplies of bottled high purity gas is eliminated.