Method for enhancement of mass resolution over a limited mass range for time-of-flight spectrometry
Novel methods and instrumentation for mass spectrometry are described. Zoom-time of flight mass spectrometry (Zoom-TOF) allows increased mass resolution over a pre-determined specific range of masses. Methods for retrofitting traditional time-of-flight (TOF) and distance of flight (DOF) mass spectrometers are described, as well as novel instruments capable of performing Zoom-TOF analyses.
1. A multi-mode mass spectrometer comprising an ion accelerator, an ion mirror, and an ion detector, wherein
in a first mode, the mass spectrometer is configured so that the ions are accelerated with constant momentum and the ion mirror is configured to reflect the ions with a linear field; and
in a second mode, the mass spectrometer is configured so that the ions are accelerated with constant energy and the ion mirror is configured to reflect the ions with a conventional field.
2. The mass spectrometer of claim 1 wherein the first mode and the second mode are switchable.
3. The mass spectrometer of claim 1 wherein the ions are accelerated from an extraction region from a substantially orthogonal ion beam.
4. The mass spectrometer of claim 1 further comprising a quadrupole doublet, where the quadrupole doublet is configured to focus an ion beam in two dimensions prior to the accelerator.
5. The mass spectrometer of claim 4 wherein the quadrupole doublet is polarized using a dc voltage.
6. The mass spectrometer of claim 5 wherein the first quadrupole of the quadrupole doublet is configured to transform the ion beam from three dimensions into substantially two dimensions.
7. The mass spectrometer of claim 5 wherein the second quadrupole of the quadrupole doublet is configured to decrease ion loss from the ion beam in two substantially orthogonal directions.
8. The mass spectrometer of claim 1 wherein the ion mirror is configured to reflect the ions towards the ion detector in a collimated beam in the first mode.
9. The mass spectrometer of claim 1 wherein the ion mirror is configured to reflect the ions towards the ion detector in a focused beam in the second mode.
10. The mass spectrometer of claim 1 wherein in the first mode the ions are included in a predetermined range of mass/charge.
11. The mass spectrometer of claim 1 wherein in the second mode the ions are included in a predetermined range of mass/charge.
12. The mass spectrometer of claim 1 wherein the detector is a time of flight detector.
13. The mass spectrometer of claim 3 wherein the extraction region comprises a plurality of parallel planar elements selected from the group consisting of:
a rear repeller element having a solid or gridded middle section;
an intermediate element having a gridded middle section;
an exit element having a gridded middle section;
one or more additional intermediate elements; and combinations thereof;
wherein insulating spacers set the distance between each of the elements; and
the planar elements are in electrical communication via a series of resistors having the voltage applied to the gridded intermediate element selectable by the operator or system.
14. A method for analyzing the mass of a sample, the method comprising the steps of
ionizing the sample into ions;
accelerating at least a portion of the ions with constant energy;
reflecting the ions with constant energy using an ion mirror having a conventional field;
detecting the ions;
accelerating a range of ions having a predetermined mass/charge with constant momentum;
reflecting the ions with constant momentum using an ion mirror having a linear field; and
detecting the range of ions.