Proteome Sciences has developed a multiplexed quantitative mass spectrometry based workflow that virtually eliminates the ratio distortion interference seen with current tandem mass spectrometry (MS2) methodologies which use isobaric labeling techniques. This represents a significant breakthrough in the evolution of mass spectrometry for use in multiplexed quantitative proteomics, and opens the door to use of this technology in a far wider range of proteomics applications for basic research, drug discovery and diagnostics.