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(11) | EP 0 575 777 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Methods of using ion trap mass spectrometers |
| (57) Improved methods of using an ion trap mass spectrometer, whereby AC voltages supplemental
to the AC trapping voltage are used for scanning the trap (10), for conducting chemical
ionization experiments, and for conducting MSn experiments, are shown. In one embodiment a broadband supplemental AC voltage is
applied to rid the trap of ions above or below a preselected cutoff mass. This is
particularly useful in conducting chemical ionization experiments for eliminating
high mass sample ions that are formed when the reagent gas is ionized by electron
impact ionization. Likewise, this technique may be used to eliminate low mass reagent
ions when conducting an electron impact ionization experiment in the presence of a
reagent gas. In another embodiment a non-resonant, low-frequency supplemental voltage
is applied to the trap (10) causing trapped ions to undergo collision induced dissociation.
Multiple generations of ion fragments may be simultaneously formed in this manner,
thereby enabling MSn experiments. The low-frequency supplemental field has the additional property of
causing high mass ions to be ejected from the trap (10) as a function of the magnitude
of the supplemental voltage. This property may be used to scan the trap (10), for
example, by scanning the magnitude of the supplemental voltage. Likewise, when conducting
chemical ionization experiments, this property may be used for eliminating unwanted
high mass sample ions, formed during ionization of the reagent gas, from the trap
(10). |