Toyoharu Okumoto

Elemental mass spectrometry using a nitrogen microwave-induced plasma as an ion source

Abstract A new mass spectrometry instrument for trace element analysis was developed that uses a 1.3 kW doughnut-shaped nitrogen high power microwave-induced plasma (MIP-MS). The fundamental analytical features of this doughnut-shaped plasma were studied. Background spectra for distilled water, nitric acid, hydrochloric acid and sulfuric acid, the acids being 1% ( v v ) aqueous solutions, were investigated. In the background spectrum for distilled water, there is no structured peak in the mass range from 49 to 90 amu where most analyte ions are distributed. As a result it is possible to determine K, Ca, Cr, Fe and Se at their major isotopes, which are interfered by polyatomic species in an argon inductively coupled plasma mass spectrometer (ICP-MS). The high power nitrogen MIP-MS exhibited single ppt to sub ppt detection limits for most elements under the multielement scanning condition. However, for the elements As and Se, which have high ionization potentials (> 9.8 eV), the detection limits exhibit high values that are one order of magnitude greater when compared with those of K, Ca and V (