Radio frequency (RF) ion guide for improved performance in mass spectrometers at high pressure
Ion guides for use in mass spectrometry (MS) systems are described. The ion guides are configured to provide a reflective electrodynamic field and a direct current (DC or static) electric field to provide ion beams that are more spatially confined with a comparatively large mass range. Some ion guides are provided between the ion source and the first stage vacuum chamber of the MS system.
1. A mass spectrometer having an inlet that is maintained, at a first pressure and a region that is maintained at a second pressure that is less than the first pressure, the inlet configured to receive an ion guide, wherein the ion guide comprises:
a substrate comprising a plurality of electrodes disposed thereover, the substrate forming a first opening at a first end and a second opening at a second end, wherein the first opening is configured to receive ions at the first pressure;
a plurality of trenches provided in the substrate, wherein each of the plurality of trenches is provided between a respective adjacent pair of the plurality of electrodes;
means for applying a radio frequency (RF) voltage between adjacent pairs of the plurality of electrodes, wherein the RF voltage creates a field in a region defined by the substrate; and
means for applying a direct current (DC) voltage drop along a length of each of the plurality of electrodes.
2. A mass spectrometer as claimed in claim 1 , wherein each of the plurality of trenches has a width, and each of the trenches has a depth, and the depth is approximately one to three times greater than the width.
3. A mass spectrometer as claimed in claim 1 , wherein the substrate is a first substrate and the plurality of electrodes is a first plurality of electrodes, the ion guide further comprising:
a second substrate comprising a second plurality of electrodes disposed thereover, the first substrate and the second substrate forming sides of the first opening at the first end and sides of the second opening at the second end.
4. A mass spectrometer as claimed in claim 3 , wherein the first opening has a first area and the second opening has a second area that is less than the first area.
5. A mass spectrometer as claimed in claim 3 , further comprising a third substrate disposed over a side wall of the ion guide and a fourth substrate disposed over another side wall of the ion guide.
6. A mass spectrometer as claimed in claim 5 , wherein the third substrate comprises a third plurality of electrodes disposed thereover, and the fourth substrate comprises a fourth plurality of electrodes disposed thereover.
7. A mass spectrometer as claimed in claim 5 , wherein the third substrate and the fourth substrate each comprise an electrically conductive material disposed over respective entire surfaces of the third and fourth substrates.
8. A mass spectrometer as claimed in claim 3 , further comprising:
means for applying, a radio frequency (RF) voltage between adjacent pairs of the secon plurality of electrodes.
9. A mass spectrometer as claimed in claim 6 , further comprising:
means for applying a radio frequency (RF) voltage between adjacent pairs of the third plurality of electrodes, and between adjacent pairs of the fourth plurality of electrodes.