Claims
- 1. A method of operating a mass spectrometer system including an ion transmission device, the method comprising:
- (i) providing a reactive gas in the ion transmission device, whereby the ion transmission device functions as a reactive collision cell;
- (ii) supplying a stream of sample ions to the reactive collision cell including desired ions to be selected and unwanted precursor ions which may react with the reaction gas to cause the formation of ions or metastables which may result, directly or indirectly through intermediate ions, in unwanted isobaric or non-spectral interferences;
- (iii) determining a range of mass-to-charge ratios of at least some of the precursor ions and intermediate ions which could result in unwanted interferences; and
- (iv) applying an appropriate field to the reactive collision cell to establish a bandpass within the reactive collision cell covering a continuous range of mass-to-charge ratios including that of said desired ions and excluding the determined range of mass-to-charge ratios of at least some of the precursor and intermediate ions.
- 2. A method as claimed in claim 1, when carried out using a multipole as the reactive collision cell.
- 3. A method as claimed in claim 2, when carried out using a quadrupole as the multipole for the reactive collision cell.
- 4. A method as claimed in claim 2 or 3, which includes applying an RF signal only to establish said bandpass within said reactive collision cell.
- 5. A method as claimed in claim 2 or 3, which includes applying both an RF signal and a DC signal to establish said bandpass within said reactive collision cell.
- 6. A method as claimed in claim 4, which includes providing the RF voltage with an amplitude of less than 500 volts peak to peak, to effect at least one of: reduction of the formation of spectral background; and loss of the desired ions due to endothermic reactions.
- 7. A method as claimed in claim 4, which includes providing the RF voltage with an amplitude of less than 200 volts peak to peak, to effect at least one of: reduction of the formation of spectral background; and loss of the desired ions due to endothermic reactions.
- 8. A method as claimed in claim 4, which includes providing the RF voltage with an amplitude in the range of 150-200 volts peak to peak, to effect at least one of: reduction of the formation of spectral background; and loss of the desired ions due to endothermic reactions.
- 9. A method as claimed in claim 4, which includes providing the RF applied to said multipole with an amplitude such as to add a selected energy to ions therein, and thereby discriminating between isobaric ions having different thermochemical properties with respect to said reaction gas.
- 10. A method as claimed in claim 2 or 3, which includes providing a broadband excitation as the means of applying said bandpass to said reactive collision cell.
- 11. A method as claimed in claim 2 or 3, which includes providing, as the means of applying said bandpass to said reactive collision cell, RF and DC to said reactive collision cell and rapidly scanning said RF and DC, with a notch in said RF and DC corresponding to said bandpass, to suppress secondary reaction of said intermediate ions.
- 12. A method as claimed in claim 1, wherein said sample ions include interfering precursor ions having the same mass as that of at least some of the selected ions, and including providing a reaction gas in said reactive collision cell to cause said interfering ions to react to form new ions of different m/z values from those of said selected ions.
- 13. A method as claimed in claim 1, wherein at least one of the intermediate and precursor ions have a first m/z value, and wherein the method includes operating the reactive collision cell with a low mass cutoff for the bandpass having an m/z value above said first m/z value.
- 14. A method as claimed in claim 1, wherein at least one of the intermediate and precursor ions have a second m/z value, and wherein the method includes operating the reactive collision cell with a high mass cutoff for the bandpass having an m/z value below said second m/z value.
- 15. A method as claimed in claim 1, wherein some of said intermediate and precursor ions have a first m/z value and others of said intermediate and precursor ions have a second m/z value which is higher than said first m/z value, and wherein the method includes operating the reactive collision cell with a bandpass covering a continuous range of m/z ratios between but excluding said first and second m/z values, whereby to transmit said selected ions and to reject at least some of said intermediate and precursor ions.
- 16. A method as claimed in claim 1, 13, 14 or 15, wherein ions from said reactive collision cell are directed into an analyzing mass spectrometer for selection, said analyzing mass spectrometer being a multipole.
- 17. A method as claimed in claim 1, 13, 14 or 15, wherein ions from said reactive collision cell are directed into an analyzing mass spectrometer for selection, said analyzing mass spectrometer being a time-of-flight mass spectrometer.
- 18. A method as claimed in claim 1, 13, 14 or 15, wherein ions from said reactive collision cell are directed into an analyzing mass spectrometer for selection, said analyzing mass spectrometer being an ion trap.
- 19. A method as claimed in claim 1, 13, 14 or 15, wherein ions from said reactive collision cell are directed into an analyzing mass spectrometer for selection, said analyzing mass spectrometer being a sector mass spectrometer.
- 20. A method as claimed in claim 1, 13, 14 or 15, and including the further steps of directing ions from said reactive collision cell into a collision cell, fragmenting ions in said collision cell to form daughter ions, and directing at least some of said daughter ions into a resolving mass analyzer for selection thereby.
- 21. A method as claimed in claim 1, 13, 13 or 15, and including the further steps of directing said ions to be selected from said reactive collision cell into an analyzing mass spectrometer, selecting ions in said analyzing mass spectrometer, and then directing ions selected in said analyzing mass spectrometer into a collision cell, fragmenting ions in said collision cell to form daughter ions, and directing at least some of said daughter ions into a resolving mass analyzer for selection thereby.
- 22. A method as claimed in claim 1, 13, 14 or 15, which includes providing the sample ions from a plasma and said reaction gas comprises gas from the plasma.
- 23. A method as claimed in any one of claims 13 to 15, including providing the reactive collision cell as a multipole.
- 24. A method as claimed in claim 1, where in the reactive collision cell includes an entrance end, through which the ions pass into the reactive collision cell, and the method comprises supplying the reaction gas into said stream of sample ions at a location in front of and spaced from said entrance end, thus to promote reactions between the reaction gas and said ions before said ions enter said reactive collision cell.
- 25. A method as claimed in claim 24, which includes injecting reaction gas at the entrance end of the multipole.
- 26. A method as claimed in claim 25, which includes injecting the reaction gas in an annular ring at said entrance end of said reactive collision cell (41).
- 27. A method as claimed in any one of claims 1, 13, 14 or 15, which includes providing ammonia as the reaction gas.
- 28. A method as claimed in any one of claims 1, 13, 14 or 15, which includes maintaining the pressure of the reaction gas in the reactive collision cell in the range 1 to 100 mTorr.
- 29. A method as claimed in claim 28, which includes maintaining the pressure of the reaction gas in the reactive collision cell in the range 5 to 30 mTorr.
- 30. A method as claimed in any one of claims 1, 13, 14 or 15, wherein the width of the bandpass is adjusted in concert with the desired ions.
- 31. A method as claimed in any one of claims 1, 13, 14 or 15, wherein the width and position of the bandpass is selected based on the chemistry of the selected reaction gas with the sample ions.
- 32. A method as claimed in any one of claims 1, 13, 14 or 15, wherein the ions supplied to said reactive collision cell are produced by an argon inductively coupled plasma.
- 33. A method as claimed in claim 32, wherein the method includes operating said reactive collision cell to remove Ar.sup.+ ions, the reaction gas reacting with the Ar+ ions to cause removal thereof.
- 34. A method as claimed in claim 32, wherein the method includes operating said reactive collision cell to reject Ar.sup.+ ions.
- 35. A method as claimed in any one of claims 1, 13, 14 or 15, which includes providing a mass filter and a detector in series with the reactive collision cell, and wherein the method includes operating said mass filter in a stability region other than the first stability region and operating said reactive collision cell in the first stability region with a high mass cutoff to reduce aliasing at said detector.
- 36. A method as claimed in claim 1, wherein the bandpass includes a high mass cutoff, thereby to limit the mass range of ions entering said time-of-flight mass spectrometer, whereby to improve the duty cycle of said time-of-flight mass spectrometer.
- 37. A method as claimed in any one of claims 1, 13, 14 or 15, wherein the reactive collision cell has an entrance end for receiving ions from a chamber having a first pressure therein and an exit for ions into a second chamber having a second pressure therein, said first pressure being greater than said second pressure, and the method including the steps of not adding reaction gas to the cell and selectively controlling the venting of said cell into said second chamber, thereby to control the pressure within the cell.
- 38. A method as claimed in claim 37, and including providing a vent in the vicinity of said exit end of said reactive collision cell into said second chamber and a mechanism for controlling the size of said vent, for selectively controlling venting in the vicinity of said exit end of said reactive collision cell into said second chamber, thereby to control pressure within the reactive collision cell.
- 39. A mass spectrometer system comprising:
- (i) an ion source for producing sample ions;
- (ii) a reactive collision cell having an entrance for receiving said sample ions, said sample ions including desired ions to be selected and unwanted precursor ions which may react with a reaction gas to cause the formation of ions or metastables which may result, directly or indirectly through intermediate ions, in unwanted isobaric or non-spectral interferences;
- (iii) means for providing the reaction gas to said reactive collision cell; and
- (iv) means for applying a field to the reactive collision cell to establish a bandpass, and for adjusting the field to select a desired bandpass range, whereby in use, said desired ions are transmitted through the reactive collision cell, and at least some of said precursor and intermediate ions which may result in unwanted isobaric or non-spectral interferences, are ejected.
- 40. A mass spectrometer system as claimed in claim 38, characterized in that the system includes at least one conduit for supplying reaction gas for mixing with the sample ions in or before the reactive collision cell.
- 41. A mass spectrometer system as claimed in claim 40, characterized in that said conduit is positioned to carry said reaction gas to a location between the ion source and the entrance of the reactive collision cell, said location being spaced upstream of said entrance.
- 42. A mass spectrometer system as claimed in claim 40 or 41, wherein said conduit includes a conduit portion for supplying reaction gas near the entrance of, but within, the reactive collision cell.
- 43. A mass spectrometer system as claimed in claim 42, wherein said conduit portion is configured to provide an annular flow of the reaction gas into the entrance of the reactive collision cell.
- 44. A mass spectrometer system as claimed in claim 39 or 43, wherein the reaction gas supply contains ammonia as a reaction gas.
- 45. A mass spectrometer system as claimed in claim 39 or 43, which includes a multipole as the reactive collision cell.
- 46. A mass spectrometer system as claimed in claim 45, wherein the multipole comprises a quadrupole.
- 47. A method of operating a mass spectrometer system in which ions are transmitted through a collision cell and into an analyzing mass spectrometer, said method comprising supplying ammonia to said collision cell as a collision gas, wherein said collision cell has an entrance for receiving ions, and wherein said ammonia is injected into said entrance end.
- 48. A method of operating a mass spectrometer system in which a stream of ions is transmitted into a collision cell, said collision cell having an entrance end, said method comprising supplying a reactive collision gas into said stream of ions at a location in front of and spaced from said entrance end, thus to promote reactions between said reactive collision gas and said ions before said ions enter said collision cell.
- 49. A method according to claim 48 wherein said reactive collision gas is additionally injected into said entrance end.
- 50. A method according to claim 49 wherein said reactive collision gas is injected in an annular ring into said entrance end of said collision cell.
- 51. A method according to claim 48, 49 or 50 wherein said reactive collision gas is ammonia.
- 52. A method according to claim 48, 49 or 50 wherein said collision cell is operated in a bandpass mode with low and high mass cutoffs, to transmit ions between said low and high mass cutoffs.
- 53. A mass spectrometer system having an ion source for producing sample ions, an ion transmission device having an entrance for receiving said sample ions, a reaction gas supply, and a conduit for carrying said reaction gas from said reaction gas supply for said reaction gas to enter said ion transmission device, and means for applying excitation to said ion transmission device to set low and high mass cutoffs therein with a bandpass therebetween, wherein said conduit is positioned to carry said reaction gas to a location between said ion source and said entrance, said location being spaced upstream of said entrance.
- 54. Apparatus according to claim 53 wherein said conduit further includes a conduit portion for carrying said reaction gas into the entrance of said ion transmission device.
- 55. Apparatus according to claim 54 wherein said conduit portion is configured to provide an annular flow of said reaction gas into said entrance of said ion transmission device.
- 56. A mass spectrometer system having an ion source for producing sample ions, an ion transmission device having an entrance for receiving said sample ions and an exit, and an analyzing mass spectrometer for receiving ions from said exit of said ion transmission device, a reaction gas supply, and a conduit for carrying said reaction gas from said reaction gas supply to the entrance of said ion transmission device, so that ions entering said ion transmission device will pass through said reaction gas as they travel into said ion transmission device.
- 57. Apparatus according to claim 56 wherein said reaction gas supply contains ammonia as a reaction gas.
- 58. A method of operating a mass spectrometer system in which sample ions are transmitted through an ion transmission device, some of said sample ions being ions which are to be selected, others of said sample ions being precursor ions which may react in said ion transmission device to cause formation of ions or metastables which may create isobaric or non-spectral interferences with said selected ions, said method comprising operating said ion transmission device to eject at least some of said precursor ions therefrom, so as to reduce said interferences, wherein said ion transmission device has an entrance for ions from a chamber having a first pressure therein and an exit for ions into a second chamber having a second pressure therein, and including the step of selectively controlling the venting of said ion transmission device into said second chamber.
- 59. A mass spectrometer system having an ion source for producing sample ions, an ion transmission device having an entrance for receiving said sample ions and an exit, and an analyzing mass spectrometer for receiving ions from said exit of said ion transmission device, a reaction gas supply, and a conduit for carrying said reaction gas from said reaction gas supply to the entrance of said ion transmission device, so that ions entering said ion transmission device will pass through said reaction gas as they travel into said ion transmission device, and including a vent at said exit end of said ion transmission device, and a mechanism for controlling the size of said vent, for selecting controlling venting at said exit end of said ion transmission device.
- 60. A method of operating a mass spectrometer system in which sample ions are transmitted through an ion transmission device, some of said sample ions being ions which are to be selected, others of said sample ions being precursor ions which may react in said ion transmission device to cause formation of ions or metastables which may create isobaric or non-spectral interferences with said selected ions, said method comprising operating said ion transmission device to eject at least some of said precursor ions therefrom, so as to reduce said interferences, wherein RF is applied to said ion transmission device, and including the step of setting the amplitude of said RF to add a selected energy to ions therein and thereby discriminating between isobaric ions having different thermochemical properties and the step of adding a reactive collision gas to said ion transmission device, said discrimination of said isobaric ions being with respect to their different thermochemical properties with respect to said reactive collision gas.
RELATED APPLICATION
This invention claims the benefit of provisional application Ser. No. 60/048,583 filed Jun. 4, 1997 and 60/074,831 filed Feb. 17, 1998 entitled "Bandpass Reactive Collision Cell".
US Referenced Citations (9)
Foreign Referenced Citations (1)
Number |
Date |
Country |
1307859 |
Dec 1988 |
CAX |