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Mass spectrometry with selective ion filtration by digital thresholding

  • US 8,987,660 B2
  • Filed: 05/07/2012
  • Issued: 03/24/2015
  • Est. Priority Date: 05/24/2004
  • Status: Expired due to Fees
First Claim
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1. A method of identifying a multiply-charged ion comprising:

  • a) specifying a first and a second digital signal thresholds on a ion identification apparatus, wherein the ion identification apparatus comprises;

    i) an ion detector;

    ii) a digitizer for converting an analog signal to a digital signal;

    iii) an analog signal transfer means for transferring an analog signal from the detector to the digitizer; and

    iv) a digital threshold filter, for setting a digital signal threshold, in digital data communication with the digitizer, in response to a digital signal input from the digitizer, independently outputting a digital signal to a data file only if the digital signal input is greater than the specified digital signal threshold;

    wherein upon an ion identification apparatus measurement of the multiply-charged ion, the filtered digital signal output to the data file originates from the detection of the multiply-charged ion and excludes digital signal output from analog signals arising from singly-charged ions;

    b) obtaining spectrum data of said multiply-charged ion at each of said first and second digital signal thresholds; and

    c) subtracting said second spectrum data from said first spectrum data to identify said multiply-charged ion as a clean isotopically resolved spectrum.

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