Patent ID: 8143066

Claim:
A method of chemical analysis, comprising: providing a complex sample comprising at least a first polypeptide and a second polypeptide; fractionating the complex sample into at least a first sample portion and a second sample portion that each include portions of the two polypeptides though in different concentration ratios; digesting the first sample portion; performing LC/MS on the digested first sample portion to observe intensities of precursor, ions associated with the first and second polypeptides in the first sample portion; digesting the second sample portion; performing LC/MS on the digested second sample portion to observe intensities of precursor ions associated with the first and second polypeptides in the second sample portion; and associating precursor ions with their corresponding one of the first and second polypeptides using ratios of the observed intensities of the precursor ions in the first and second sample portions.