¹³C/¹⁵N/D-labeled synthetic peptides are typically used as standards and reagents in mass spectrometry or Nuclear Magnetic Resonance-based applications.

They are synthesized using the solid-phase peptide synthesis using stable isotope enriched protected (Fmoc or tBoc) amino-acids. The use of labeled synthetic peptides plays a central role in discovery, characterization and quantification of proteins when using approaches such as AQUA, PSAQ method and QconCAT methods.