458. surface plasmon resonance (SPR) Change of the reflective index of light reflected off a metallic film resulting from biomolecular binding on the opposite side of the film.
459. surrogate analyte A compound similar to the analyte of interest used to evaluate extraction efficiency and matrix effects (e.g., stable-labeled isotope analogs).
460. surrogate matrix Alternative matrix used in bioanalysis in place of an endogenous matrix that is difficult to sample, recreate or maintain.
461. surrogate peptide In protein LC–MS bioanalysis, the preferred term used to describe the unique peptide derived from the proteolytic digestion of a specific protein analyte, which is then used to quantify the protein by LC–MS/MS. Other terms, such as target peptide and analytical peptide, have been used to describe this type of peptide. In specific cases mass spectrometry methods other than MS/MS may be applied.
