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 investigate d as an ion source for time-of-flight mass spectrometry. The first sta ge 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 t he mass spectrometer enables the relative energies of the extracted io ns to be determined; the energies of the argon support gas and analyte ions were compared. The figures of merit for the system were investig ated, 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 init ial survey of the major spectral interferents, the relative sensitivit ies for different elements were determined. The source was also operat ed at low pressures (0.01 Torr) in order to determine whether operatin g in this pressure regime can be used to alleviate polyatomic interfer ences.