Atmospheric analysis using a microwave plasma ionization source and ion trap mass spectrometry

The on-line detection of both positive and negative ions has been demonstrated using a microwave plasma ionization source coupled with an ion trap mass spectrometer. Real-time xenon and krypton isotope measurements in air were made using either supplemental helium or atmospheric argon for plasma generation. The halogen signature from an organic molecule was detected as a negative ion using a helium plasma. Two instrument configurations have been assembled, one combining a microwave plasma source, an injection lens, and the ion trap; in the second assembly, a radiofrequency-only quadrupole mass filter was inserted between the lens and the ion trap. Most of the data reported here were acquired with the first configuration, although preliminary data with the second configuration has been taken. General operating parameters are discussed. The precision of xenon isotope ratio measurements ranged from 0.8% to 5% relative standard deviation, depending on the magnitude of the ratio. (Int J Mass Spectrom 178 (1998) 121-128) (C) 1998 Elsevier Science B.V.