Bioanalysis of biotherapeutic proteins and peptides: immunological or MS approach? "When peptide bioanalysis is required, LC-MS/MS could be the analytical method of choice unless the required sensitivity is unattainable ... it remains to be seen whether MS can supplant immunoassays for large-molecule analysis in much the same way that ELISAs supplanted RIAs in the 1980s, but the tools are available."