| 摘要 |
A mass spectrometer with an ionizing chamber in which either of an NCI ion source for producing negative ions and a PCI ion source for producing positive ions is placed. The NCI ion source has a first gas inlet and a second gas inlet, while the PCI ion source has only one gas inlet. In the wall of the ionizing chamber are provided a sample gas inlet and a reaction gas inlet. At an end of the sample gas inlet inside of the ionizing chamber is provided a splitter having a first branch and a second branch. When the NCI ion source is placed in the ionizing chamber, the first gas inlet is connected to the first branch, the second gas inlet is connected to the reaction gas inlet inside of the ionizing chamber, and the second branch is left unconnected inside of the ionizing chamber. By adequately adjusting the flow resistances of the first and second branches, a desired portion of the reference gas from the sample gas source can be supplied to the NCI ion source when a calibration is performed. After the calibration is finished, the residual gas and ions in the NCI ion source are evacuated to the ionizing chamber through the first gas inlet, first branch and second branch. When the PCI ion source is placed in the ionizing chamber, the sole gas inlet is connected to the first branch, and the second branch is connected to the reaction gas inlet. The reference gas and the reaction gas are mixed together at the splitter and delivered to the PCI ion source.
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