Helium-argon inductively coupled plasma for plasma source mass spectrometry

Abstract

An He-Ar mixed gas inductively coupled plasma (ICP) was investigated for use as an ion source for plasma mass spectrometry (MS). The addition of He to Ar produces a plasma capable of ionising high ionisation potential elements more efficiently than the pure Ar plasma. The best signal to noise ratios for metallic elements were obtained with a 20% He plasma, and for halides with a 30% He plasma. The He-Ar mixed gas plasma shows an improvement of one order of magnitude in the detection limits of several metallic elements studied and an improvement of two orders of magnitude for non-metals in comparison with Ar ICP-MS. Figures of merit, including detection limits, linear dynamic ranges, metal oxide ratios and doubly to singly charged ion ratios, are reported and compared with those for Ar ICP-MS.