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 method of determining the amount of a species in a sample, the method comprising:
measuring a non-saturated analog signal representative of the species in the sample, in which the non-saturated analog signal is measured with an electron multiplier comprising a plurality of dynodes in which at least two dynodes of the plurality of dynodes are electrically coupled to a respective electrometer, in which the electron multiplier is configured to terminate signal amplification at a dynode where a saturation current is detected, in which the electron multiplier is configured to split a beam into a first beam and a second beam, in which the electron multiplier is electrically coupled to a processor configured to measure the non-saturated analog signal using the first beam and one of the at least two dynodes electrically coupled to its respective electrometer;
counting pulses using the second beam and the processor to provide a pulse count signal; and
cross-calibrating the measured, non-saturated analog signal and the provided pulse count signal using the processor to determine the amount of species in the sample.
2. The method of claim 1 , in which the electron multiplier is configured to receive ions after ionization of the species in the sample.
3. The method of claim 1 , in which the electron multiplier is configured to receive photons emitted by the species in the sample.
4. The method of claim 1 , further comprising measuring the non-saturated analog signal at a dynode immediately upstream of the dynode where the saturation current is detected using the processor.
5. The method of claim 1 , further comprising measuring the non-saturated analog signal at a dynode at least two dynodes upstream of the dynode where the saturation current is detected using the processor.
6. The method of claim 1 , further comprising measuring a second non-saturated analog signal at a different dynode than where the non-saturated analog signal is measured, and cross-calibrating the measured, second non-saturated analog signal with the provided pulse count signal using the processor.
7. The method of claim 6 , further comprising measuring a third non-saturated analog signal at a different dynode than where the non-saturated analog signal and the second, non-saturated analog signal are measured, and cross-calibrating the measured, third non-saturated analog signal with the provided pulse count signal using the processor.
8. The method of claim 1 , further comprising measuring additional analog signals from each dynode between dynodes that provide an analog signal above a noise signal and below a saturation signal, and cross-calibrating each of the measured additional analog signals with the provided pulse count signal using the processor.
9. The method of claim 8 , in which the additional analog signal from each dynode is converted to a digital signal that is cross-calibrated with the provided pulse count signal.
10. The method of claim 8 , further comprising detecting second species in the sample, different from the species in the sample, without adjusting the voltage of the electron multiplier by measuring a non-saturated analog signal representative of the second species in the sample using the processor, and cross-calibrating the measured non-saturated analog signal representative of the second species in the sample and the pulse count signal to determine the amount of second species in the sample using the processor.
11. The method of claim 1 , wherein each of the plurality of dynodes is electrically coupled to a respective electrometer.
12. The method of claim 11 , wherein each respective electrometer is electrically coupled to a signal converter.
13. The method of claim 12 , in which each of the respective signal converters is an analog-to-digital converter.
14. The method of claim 13 , in which each of the analog-to-digital converters is electrically coupled to the processor.
15. The method of claim 11 , wherein the plurality of dynodes and each respective electrometer are in the same housing.