Detectors and methods of using them
View Patent ↗Certain embodiments described herein are directed to detectors and systems using them. In some examples, the detector can include a plurality of dynodes, in which one or more of the dynodes are coupled to an electrometer. In some instances, an analog signal from a non-saturated dynode is measured and cross-calibrated with a pulse count signal to extend the dynamic range of the detector.
1. A mass spectrometer comprising:
a sample introduction system;
an ion source fluidically coupled to the sample introduction system;
a mass analyzer fluidically coupled to the ion source; and
a single detector fluidically coupled to the mass analyzer and configured to split a beam received from the mass analyzer into a first beam and a second beam, in which the single detector comprises a plurality of dynodes, in which at least two dynodes of the plurality of dynodes are each electrically coupled to a respective electrometer, in which the single detector comprises a processor configured to measure a non-saturated analog signal, using the first beam, from one of the at least two dynodes electrically coupled to its respective electrometer, in which the single detector is configured to count pulses, using the second beam, to provide a pulse count signal, and in which the processor is configured to cross-calibrate the measured non-saturated analog signal with the pulse count signal to provide a calibration curve.
2. The mass spectrometer of claim 1 , further comprising at least one additional electrometer electrically coupled to one of the plurality of dynodes.
3. The mass spectrometer of claim 2 , further comprising a respective processor electrically coupled to each electrometer.
4. The mass spectrometer of claim 3 , in which at least one dynode without a respective electrometer is positioned between dynodes that are electrically coupled to an electrometer.
5. The mass spectrometer of claim 1 , further comprising a plurality of electrometers, in which the electron multiplier is configured with every other dynode electrically coupled to an electrometer.
6. The mass spectrometer of claim 1 , further comprising a plurality of electrometers, in which the electron multiplier is configured with every third dynode electrically coupled to an electrometer.
7. The mass spectrometer of claim 1 , further comprising a plurality of electrometers, in which the electron multiplier is configured with every fourth dynode electrically coupled to an electrometer.
8. The mass spectrometer of claim 1 , further comprising a plurality of electrometers, in which the electron multiplier is configured with every fifth dynode electrically coupled to an electrometer.
9. The mass spectrometer of claim 3 , in which each electrometer is electrically coupled to a signal converter.
10. The mass spectrometer of claim 9 , in which each electrometer is electrically coupled to an analog-to-digital converter to provide simultaneous digital signals to the respective processor from each of the dynodes electrically coupled to an electrometer.
11. The mass spectrometer of claim 10 , in which the respective processor is configured to cross-calibrate the non-saturated analog signal with the pulse count signal.
12. The mass spectrometer of claim 1 , in which the processor is electrically coupled to each of the plurality of dynodes and configured to prevent a current overload at each dynode.
13. The mass spectrometer of claim 12 , in which the processor is configured to alter the voltage at a saturated dynode or a dynode downstream from the saturated dynode.
14. The mass spectrometer of claim 11 , in which voltage of the electron multiplier is not adjusted between measuring species having different mass-to-charge ratios and/or different concentrations.
15. The mass spectrometer of claim 1 , in which the electron multiplier is configured to terminate signal amplification at a saturated dynode of the plurality of dynodes.
16. The mass spectrometer of claim 1 , in which the electron multiplier is configured to provide independent voltage control at each dynode of the plurality of dynodes.
17. The mass spectrometer of claim 1 , in which dynode to dynode voltage is constant with a change of electron current at each dynode.
18. The mass spectrometer of claim 1 , in which dynamic range of ion current measurement is greater than 10 8 for a 100 KHz reading.
19. The mass spectrometer of claim 1 , in which the processor is configured to use the non-saturated analog signal the pulse count signal and the provided calibration curve to determine the level of ions in a sample.
20. The mass spectrometer of claim 19 , in which the processor is configured to scale the non-saturated analog signal using a respective electron multiplier gain.