title: A stable-isotope HPLC-MS/MS method to simplify storage of human whole blood samples for glutathione assay.
abstract: BACKGROUND
  Glutathione is the principal non-protein tripeptide thiol present in most mammalian cells and plays an important role in the redox status of biological systems. The accurate assessment of reduced glutathione (GSH) status as a reliable index of oxidative stress is of research and clinical significance. GSH undergoes rapid oxidation after sample collection and this presents a challenge.
  
  
  METHODS
  Validation of an HPLC-MS/MS assay is reported. Storage stability using four variants of a methanolic precipitation with addition of stable isotope internal standard at collection is compared to L-serine borate/EDTA with perchloric acid precipitation (SBPE).
  
  
  RESULTS
  Precipitation with methanol and addition of stable isotope on sample collection, combined with storage in solution at -70 °C showed superior storage stability to SBPE and other variants of the methanolic precipitation method up to 99 days.
  
  
  CONCLUSIONS
  The combination of stable isotope with methanolic precipitation at collection, with assay by HPLC-MS/MS provides superior results after storage of whole blood samples for at least 99 days.
authors.affiliation: Australian Centre for Paediatric Pharmacokinetics, Mater Medical Research Institute, Raymond Terrace, South Brisbane 4101, Qld, Australia. ross.norris@mater.org.au
authors.forename: R L G
authors.initials: RL
authors.lastname: Norris
authors.forename: M
authors.initials: M
authors.lastname: Paul
authors.forename: R
authors.initials: R
authors.lastname: George
authors.forename: A
authors.initials: A
authors.lastname: Moore
authors.forename: R
authors.initials: R
authors.lastname: Pinkerton
authors.forename: A
authors.initials: A
authors.lastname: Haywood
authors.forename: B
authors.initials: B
authors.lastname: Charles
mesh_terms: D001800:Blood Specimen Collection; D002247:Carbon Isotopes; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005978:Glutathione / Q000097:blood* / Q000737:chemistry*; D006801:Humans; D000432:Methanol / Q000737:chemistry; D009587:Nitrogen Isotopes; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D005978:Glutathione; D000432:Methanol