title: Stable isotopically labeled internal standards in quantitative bioanalysis using liquid chromatography/mass spectrometry: necessity or not?
abstract: It appears to be a general belief that stable isotopically labeled (SIL) internal standards yield better assay performance results for quantitative bioanalytical liquid chromatography/mass spectrometry (LC/MS) assays than does any other internal standard. In this article we describe our experiences with structural analogues and SIL internal standards and their merits and demerits. SIL internal standards are the first choice, but deuterium-labeled compounds may demonstrate unexpected behavior, such as different retention times or recoveries, than the analyte. In addition, a SIL internal standard with identical chemical properties as the analyte may cover up assay problems with stability, recovery, and ion suppression. Since SIL internal standards are not always available or are very expensive, structural analogues can be used, however, with consideration of several issues, which are usually displayed during method validation.
authors.affiliation: Department of Pharmacy & Pharmacology, Slotervaart Hospital/The Netherlands Cancer Institute, Louwesweg 6, 1066 EC Amsterdam, The Netherlands.
authors.forename: Ellen
authors.initials: E
authors.lastname: Stokvis
authors.forename: Hilde
authors.initials: H
authors.lastname: Rosing
authors.forename: Jos H
authors.initials: JH
authors.lastname: Beijnen
mesh_terms: D000081:Acetamides / Q000032:analysis; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000032:analysis*; D000970:Antineoplastic Agents / Q000032:analysis*; D047630:Depsipeptides / Q000032:analysis; D004355:Drug Stability; D004791:Enzyme Inhibitors / Q000032:analysis; D005559:Formamides / Q000032:analysis; D007211:Indoles / Q000032:analysis; D007553:Isotope Labeling; D007783:Lactones / Q000032:analysis*; D061965:Matrix Metalloproteinase Inhibitors; D008978:Mollusk Venoms / Q000032:analysis; D012015:Reference Standards; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods* / Q000592:standards*; D013450:Sulfones / Q000032:analysis*
chemical_list: D000081:Acetamides; D000894:Anti-Inflammatory Agents, Non-Steroidal; D000970:Antineoplastic Agents; D047630:Depsipeptides; D004791:Enzyme Inhibitors; D005559:Formamides; D007211:Indoles; D007783:Lactones; D061965:Matrix Metalloproteinase Inhibitors; D008978:Mollusk Venoms; C443806:N-(1-(2,2-dimethyl-1,3-dioxol-4-yl)-2-((4,4-(trifluoromethoxyphenoxy)phenyl)sulfonyl)ethyl)-N-hydroxyformamide; D013450:Sulfones; C116926:rofecoxib; C419187:indibulin; C097897:kahalalide F