Apparatus and method for ion separation
Disclosed herein are systems and methods for sorting ions including a group of multipole electrodes configured to form an ion trap, and an ion guide adjacent to, and operably coupled to the group of multipole electrodes. Using a radio frequency (RF) or Direct Current (CD) power supply device the system can apply an RF voltage to the group of multipole electrodes thereby creating a pseudo-potential barrier. A DC gradient voltage may then be applied creating an axial field in opposition to the pseudo-potential barrier. As the DC voltage is raised and/or the RF voltage is lowered, one or more ions will be eluted through the barrier.
1 . A system for sorting ions comprising:
a group of multipole electrodes configured to form an ion trap, wherein the group of multipole electrodes comprise a group of quadrupole electrodes, wherein the group of quadrupole electrodes comprise:
a first inner electrode and a first outer electrode, and
a second inner electrode and a second outer electrode;
an ion guide adjacent to the second inner electrode and the second outer electrode; and
a RF and DC voltage device configured to apply a first RF voltage to the first inner electrode and the first outer electrode creating a first pseudo-potential barrier disposed between the first inner electrode and the first outer electrode, a second RF voltage to the second inner electrode and the second outer electrode creating a second pseudo-potential barrier disposed between the second inner electrode and the second outer electrode, and apply a DC voltage creating an axial field in opposition to the first pseudo-potential barrier or the second pseudopotential barrier, wherein the first pseudo-potential barrier and the second pseudo-potential barrier are each independently configured to confine one or more ions in an annulus disposed between the first inner electrode, the first outer electrode, the second inner electrode, and the second outer electrode; and
wherein ramping at least one of the first RF voltage, second RF voltage, DC voltage, or a combination thereof causes at least one of the one or more ions to be eluted across the second pseudo-potential barrier,
wherein the ion guide is an ion funnel.
2 . The system of claim 1 , wherein the group of quadrupole electrodes are configured to provide a quadrupolar potential.
3 . The system of claim 1 , wherein eluting at least one of the one or more ions across the second pseudo-potential barrier further comprises increasing the axial DC field to initiate axial stratification in the ion trap and elute the ions across the second pseudo-potential barrier based substantially on their mass-to-charge ratio.
4 . The system of claim 1 , wherein ramping the second RF voltage involves decreasing the second RF voltage to initiate axial stratification in the ion trap and elute the ions across the second pseudo-potential barrier based on their mass-to-charge ratio.
5 . The system of claim 1 , wherein eluting at least one of the one or more ions across the second pseudo-potential barrier further comprises floating the ion trap with respect to an entrance potential of the ion guide to elute the ions across the second pseudo-potential barrier based on their mass-to-charge ratio.
6 . The system of claim 1 , wherein eluting at least one of the one or more ions across the second pseudo-potential barrier further comprises at least one of:
increasing the DC voltage and decreasing the second RF voltage;
increasing the DC voltage and floating the ion trap with respect to the ion guide;
decreasing the second RF voltage and floating the ion trap with respect to the ion guide; or
increasing the DC voltage, decreasing the second RF voltage applied to the group of electrodes, and floating the ion trap with respect to the ion guide.
7 . The system of claim 1 , wherein the ions are substantially unconfined or unrestrained in a tangential direction which is orthogonal both to a radial direction and to a longitudinal axis of the ion guide or ion trap.
8 . The system of claim 1 , wherein the system operates between 1 mTorr and 5 Torr.
9 . The system of claim 1 , wherein the RF voltage has a frequency selected from the group consisting of: (i) <100 kHz; (ii) 100-200 kHz; (iii) 200-300 kHz; (iv) 300-400 kHz; (v) 400-500 kHz; (vi) 0.5-1.0 MHz; (vii) 1.0-1.5 MHz; (viii) 1.5-2.0 MHz; (ix) 2.0-2.5 MHz; (x) 2.5-3.0 MHz; (xi) 3.0-3.5 MHz; (xii) 3.5-4.0 MHz; (xiii) 4.0-4.5 MHz; (xiv) 4.5-5.0 MHz; (xv) 5.0-5.5 MHz; (xvi) 5.5-6.0 MHz; (xvii) 6.0-6.5 MHz; (xviii) 6.5-7.0 MHz; (xix) 7.0-7.5 MHz; (xx) 7.5-8.0 MHz; (xxi) 8.0-8.5 MHz; (xxii) 8.5-9.0 MHz; (xxiii) 9.0-9.5 MHz; (xxiv) 9.5-10.0 MHz; and (xxv) >10.0 MHz; and
(b) the RF voltage has an amplitude selected from the group consisting of: (i) <50 V peak to peak; (ii) 50-100 V peak to peak; (iii) 100-150 V peak to peak; (iv) 150-200 V peak to peak; (v) 200-300 V peak to peak; (vi) 300-400 V peak to peak; (vii) 400-500 V peak to peak; (viii) 500-600 V peak to peak; (ix) 600-700 V peak to peak; (x) 700-800 V peak to peak; (xi) 800-900 V peak to peak; (xii) 900-1000 V peak to peak; (xiii) 1000-1100 V peak to peak; (xiv) 1100-1200 V peak to peak; (xv) 1200-1300 V peak to peak; (xvi) 1300-1400 V peak to peak; (xvii) 1400-1500 V peak to peak; and (xviii) >1500 V peak to peak.
10 . A method for sorting ions comprising:
applying, using a RF and DC voltage device, a first RF voltage to a first inner electrode and a first outer electrode of a group of multipole electrodes creating a first pseudo-potential barrier disposed between the first inner electrode and the first outer electrode;
applying, using the RF and DC voltage device, a second RF voltage to a second inner electrode and a second outer electrode of the group of multipole electrodes creating a second pseudo-potential barrier disposed between the second inner electrode and the second outer electrode;
applying, using the RF and DC voltage device, a DC voltage creating an axial field in opposition to the first pseudo-potential barrier or the second pseudo-potential barrier, wherein the first pseudo-potential barrier and the second pseudo-potential barrier are independently configured to confine one or more ions in an annulus disposed between the first inner electrode, the first outer electrode, the second inner electrode, and the second outer electrode; and
ramping at least one of the first RF voltage, second RF voltage, DC voltage, or a combination thereof causing at least one of the one or more ions to be eluted across the second pseudo-potential barrier to an ion guide adjacent to the group of multipole electrodes, wherein the ion guide is an ion funnel.
11 . The method of claim 10 , wherein the group of multipole electrodes comprise a group of quadrupole electrodes configured to provide a quadrupolar potential.
12 . The method of claim 10 , wherein eluting at least one of the one or more ions across the second pseudo-potential barrier further comprises increasing the axial field to initiate axial stratification in the ion trap and elute the ions across the second pseudo-potential barrier based on their mass-to-charge ratio.
13 . The method of claim 10 , wherein ramping the second RF voltage involves decreasing the second RF voltage applied to the group of electrodes to initiate axial stratification in the ion trap and elute the ions across the second pseudo-potential barrier based on their mass-to-charge ratio.
14 . The method of claim 10 , wherein eluting at least one of the one or more ions across the second pseudo-potential barrier further comprises floating the ion trap with respect to an entrance potential of the ion guide to elute the ions across the second pseudo-potential barrier based on their mass-to-charge ratio.
15 . The method of claim 10 , wherein eluting at least one of the one or more ions across the pseudo-potential barrier further comprises at least one of:
increasing the DC voltage and decreasing the second RF voltage;
increasing the DC voltage and floating the ion trap with respect to the ion guide;
decreasing the second RF voltage and floating the ion trap with respect to the ion guide; or
increasing the DC voltage, decreasing the second RF voltage, and floating the ion trap with respect to the ion guide.
16 . The method of claim 10 , wherein the ions are substantially unconfined or unrestrained in a tangential direction which is orthogonal both to a radial direction and to a longitudinal axis of the ion guide or ion trap.
17 . The method of claim 10 , wherein the system operates between 1 mTorr and 5 Torr.
18 . The method of claim 10 , wherein the RF voltage has a frequency selected from the group consisting of: (i) <100 kHz; (ii) 100-200 kHz; (iii) 200-300 kHz; (iv) 300-400 kHz; (v) 400-500 kHz; (vi) 0.5-1.0 MHz; (vii) 1.0-1.5 MHz; (viii) 1.5-2.0 MHz; (ix) 2.0-2.5 MHz; (x) 2.5-3.0 MHz; (xi) 3.0-3.5 MHz; (xii) 3.5-4.0 MHz; (xiii) 4.0-4.5 MHz; (xiv) 4.5-5.0 MHz; (xv) 5.0-5.5 MHz; (xvi) 5.5-6.0 MHz; (xvii) 6.0-6.5 MHz; (xviii) 6.5-7.0 MHz; (xix) 7.0-7.5 MHz; (xx) 7.5-8.0 MHz; (xxi) 8.0-8.5 MHz; (xxii) 8.5-9.0 MHz; (xxiii) 9.0-9.5 MHz; (xxiv) 9.5-10.0 MHz; and (xxv) >10.0 MHz; and
(b) the RF voltage has an amplitude selected from the group consisting of: (i) <50 V peak to peak; (ii) 50-100 V peak to peak; (iii) 100-150 V peak to peak; (iv) 150-200 V peak to peak; (v) 200-300 V peak to peak; (vi) 300-400 V peak to peak; (vii) 400-500 V peak to peak; (viii) 500-600 V peak to peak; (ix) 600-700 V peak to peak; (x) 700-800 V peak to peak; (xi) 800-900 V peak to peak; (xii) 900-1000 V peak to peak; (xiii) 1000-1100 V peak to peak; (xiv) 1100-1200 V peak to peak; (xv) 1200-1300 V peak to peak; (xvi) 1300-1400 V peak to peak; (xvii) 1400-1500 V peak to peak; and (xviii) >1500 V peak to peak.