Isotope dilution assay in peptide quantification: The challenge of microheterogeneity of internal standard

Alexander V. Stoyanov, Eduard Rogatsky, Daniel Stein, Shawn Connolly, Curt L. Rohlfing, Randie R. Little

Research output: Contribution to journalArticle

5 Scopus citations


Isotope dilution analysis allows quantitation of elements and different compounds in complex mixtures. The quantitation is based on a known amount of reference material (internal standard, IS) added to a sample that makes the result critically dependent on the value assigned to the standard. In the case of peptides, IS concentration is determined by nitrogen and amino acid analysis while purity is normally assessed by methods such as chromatography or electrophoresis that might not be able to detect many possible amino acid modifications, either naturally occurring or chemically induced. Microheterogeneity of the IS, if it is not accounted for when assigning a reference value to the standard, results in highly overestimated values in target analyte quantitation. In this viewpoint article, we illustrate the problem of internal standard microheterogeneity by analyzing synthetic human C-peptide labeled analogs.

Original languageEnglish (US)
Pages (from-to)825-828
Number of pages4
JournalProteomics - Clinical Applications
Issue number11-12
StatePublished - Dec 1 2013



  • C-peptide
  • Isotope dilution assay
  • Microheterogeneity
  • Reference material

ASJC Scopus subject areas

  • Clinical Biochemistry

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