title: Quantification of intact human insulin-like growth factor-I in serum by nano-ultrahigh-performance liquid chromatography/tandem mass spectrometry.
abstract: BACKGROUND
  Insulin-like growth factor-I is one of the biomarkers used to detect growth hormone administration prohibited in human sport. Current testing approaches for IGF-I rely on commercial immunoassays, which may change from time to time requiring complex revalidation. Mass spectrometry (MS)-based approaches often rely on enzymatically digesting the protein and measuring specific peptide concentrations. In order to reinforce the current available methodology for IGF-I testing, a reliable and equally sensitive MS method is required for the analysis of intact protein using small sample volumes (<25 μL).
  
  
  METHODS
  IGF-I was extracted from human serum samples by a simple protein precipitation procedure. Separation was achieved via nano-ultrahigh-performance liquid chromatography and MS analysis was conducted by nano-electrospray ionisation triple-quadrupole mass spectrometry in the selected reaction monitoring mode using a stable-isotope-labelled internal standard.
  
  
  RESULTS
  A six-point calibration curve ranging from 50 to 1000 ng/mL of human IGF-I in rat serum was used to establish instrument response. The method provided a limit of quantification of 50 ng/mL, with intra- and inter-day precision ≤5% and intra- and inter-day accuracy ≥95%.
  
  
  CONCLUSIONS
  A quantitative method was developed for the quantification of intact IGF-I in human serum samples. The data generated provided important information for the development of a new reference method for the growth hormone biomarker test and helped create a reliable system for monitoring peptide hormones in individual athletes, a possible extension to the athlete biological passport system. Nano-electrospray has here been shown to be sufficiently robust for routine use in an analytical laboratory, allowing for the analysis of minute sample volumes.
authors.affiliation: King's College London, Analytical and Environmental Science Division, Drug Control Centre, 150 Stamford Street, London, SE1 9NH, UK.
authors.forename: Filipe
authors.initials: F
authors.lastname: Lopes
authors.forename: David A
authors.initials: DA
authors.lastname: Cowan
authors.forename: Mario
authors.initials: M
authors.lastname: Thevis
authors.forename: Andreas
authors.initials: A
authors.lastname: Thomas
authors.forename: Mark C
authors.initials: MC
authors.lastname: Parkin
mesh_terms: D000818:Animals; D002138:Calibration; D002851:Chromatography, High Pressure Liquid / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D016014:Linear Models; D036103:Nanotechnology / Q000295:instrumentation*; D051381:Rats; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000295:instrumentation / Q000379:methods*
chemical_list: D007334:Insulin-Like Growth Factor I