RADIO-FREQUENCY-POWERED PLANAR-MAGNETRON GLOW-DISCHARGE AS A SOURCE FOR TIME-OF-PLIGHT ELEMENTAL MASS-SPECTROMETRY

A radio-frequency (rf) planar-magnetron glow discharge was investigated as an ion source for time-of-flight mass spectrometry. The first stage of a conventional ICP-MS interface was modified to create a planar-magnetron glow-discharge cell. The pressure and power of the magnetron source were optimized for ion signal. The perpendicular geometry of the mass spectrometer enables the relative energies of the extracted ions to be determined; the energies of the argon support gas and analyte ions were compared. The figures of merit for the system were investigated, and detection limits of 0.1-1 ppm were achieved for elements in a conducting matrix. Detection limits were an order of magnitude worse for elements in an electrically insulating sample. Along with an initial survey of the major spectral interferents, the relative sensitivities for different elements were determined. The source was also operated at low pressures (0.01 Torr) in order to determine whether operating in this pressure regime can be used to alleviate polyatomic interferences.