Analysis of data from a mass spectrometer

Abstract

A programmed computer analyzes data from a mass spectrometer. A spectrum corresponding to an unknown sample is perturbed in various ways, and each perturbed spectrum is compared with the spectrum of a known or reference substance. The perturbed spectrum having the highest correlation with the known spectrum, and which is also physically plausible, is considered to be the best fit. The method indicates in what specific ways the unknown sample differs from, or is similar to, the known substance.

1 . A method of analyzing data from a mass spectrometer, comprising: 
 a) generating a plurality of first mass spectra corresponding to a known sample during a selected time interval, and a plurality of second mass spectra corresponding to an unknown sample and obtained during said time interval,    b) comparing candidate second mass spectra with said plurality of first mass spectra, and    c) selecting for further study, a candidate second mass spectrum which contains components which are not in common with components in said first mass spectra.    
   
   
       2 . The method of  claim 1 , wherein the comparing step comprises computing correlations between said candidate second mass spectra and said plurality of first mass spectra, and wherein a candidate second mass spectrum is selected if all correlations between said candidate second mass spectrum and said first mass spectra are below a predetermined threshold.  
   
   
       3 . The method of  claim 1 , wherein the comparing step comprises computing correlations between said candidate second mass spectra and said plurality of first mass spectra, and computing a signal ratio defined as a ratio of a total signal for said candidate second mass spectrum to a total signal for each of said first mass spectra, and wherein a candidate second mass spectrum is selected if any correlations between said candidate second mass spectrum and said first mass spectra are above a predetermined threshold and the corresponding signal ratio is above a predetermined level.  
   
   
       4 . The method of  claim 1 , wherein step (c) comprises determining whether there are any MS/MS spectra among said first spectra having a same parent mass as in a member of said second spectra, and selecting said member if there are no such MS/MS spectra.  
   
   
       5 . The method of  claim 1 , wherein the comparing step comprises computing correlations between said candidate second mass spectra and said plurality of first mass spectra, and computing a signal ratio defined as a ratio of a total signal for said candidate second mass spectrum to a total signal for each of said first mass spectra, 
 and wherein step (c) includes rejecting a candidate second mass spectrum if all comparisons between said candidate second mass spectrum and said first mass spectra do not result in a correlation above a predetermined threshold and a signal ratio above a predetermined level, and there is at least one occurrence of both a high correlation value and a low signal ratio among said comparisons.