Method of high mass resolution scanning of an ion trap mass spectrometer

A method of using an ion trap mass spectrometer comprising the steps of:

• (a) establishing a trapping field within the ion trap such that ions in a range of interest are stably held within the ion trap;
• (b) introducing a sample matrix into the ion trap and ionizing the sample matrix such that sample ions are trapped within the ion trap;
• (c) resonantly ejecting all ions within the trap that do not fall within a selected narrow mass range, thereby eliminating sources of space charge which interfere with high resolution mass analysis;
• (d) slowly scanning the ion trap to sequentially eject ions within said selected narrow mass range;
• and,
• (e) detecting the ions ejected from the ion trap.

A method of using a quadrupole ion trap mass spectrometer comprising the steps of:

• (a) establishing a trapping field within the ion trap such that ions in a range of interest are stably held within the ion trap;
• (b) introducing a sample matrix into the ion trap, said sample matrix comprising ions within said range of interest;
• (c) introducing a reference compound into the ion trap, said reference compound comprising ions within said range of interest;
• (d) ionizing the sample matrix and the reference compound, such that sample ions and reference ions are trapped within the ion trap;
• (e) resonantly ejecting all ions from the ion trap that do not fall within any of at least two selected narrow mass ranges, said first selected mass range including the mass of sample ions of interest and said second mass range including the mass of said reference compound, thereby eliminating sources of space charge which interfere with high resolution mass analysis;
• (f) scanning the ion trap to eject ions within said selected narrow mass ranges;
• and,
• (g) detecting the ions ejected from the ion trap during step (f).

A method of using a quadrupole ion trap mass spectrometer comprising the steps of:

• (a) establishing a trapping field within the ion trap such that ions in a range of interest are stably held within the ion trap;
• (b) introducing a sample matrix into the ion trap;
• (c) introducing a reference compound into the ion trap;
• (d) ionizing the sample matrix and the reference compound, such that sample ions and reference ions are trapped within the ion trap;
• said step of ionizing comprising applying a first broadband ejection signal to said ion trap during a first ionization period t.sub.1, said first broadband signal having frequency components necessary to eject all but said sample ions from the ion trap, and thereafter applying a second broadband ejection signal to said ion trap during a second ionization period t.sub.2, said second broadband signal having frequency components necessary to eject all but said sample ions and said reference ions from the ion trap, such that all ions in the ion trap fall within two selected narrow mass ranges, said first selected mass range including the mass of sample ions of interest and said second mass range including the mass of said reference compound;
• (e) scanning the ion trap to eject ions within said selected narrow mass ranges;
• and,
• (f) detecting the ions ejected from the ion trap during step (e).