title: A novel method for the measurement of plasma metanephrines using online solid phase extraction-liquid chromatography tandem mass spectrometry.
abstract: BACKGROUND
  Measurement of plasma metanephrine, normetanephrine and 3-methoxytyramine is useful in the diagnosis of phaeochromocytomas, but many assays require a large volume of plasma due to poor assay sensitivity, and often require lengthy sample preparation. Our aim was to develop a method for measurement of plasma metanephrines using a small sample volume with minimal hands-on preparation.
  
  
  METHODS
  Samples were deproteinised using 10 K spin filters prior to online solid phase extraction using a Waters Acquity UPLC Online SPE Manager (Waters, Manchester, UK) coupled to a Waters Xevo TQ-S mass spectrometer (Waters, Manchester, UK). The assay was validated and results compared to a previously published method.
  
  
  RESULTS
  We achieved a limit of quantification of 37.5 pmol/L for metanephrine and 3-methoxytyramine and 75 pmol/L for normetanephrine using only 150 µL of sample. The assay was linear up to 30,000 pmol/L for all analytes and in a method comparison study results showed good agreement with a previously published LC-MS/MS assay.
  
  
  CONCLUSIONS
  We have developed a simple method for measurement of plasma metanephrine, normetanephrine and 3-methoxytyramine using only 150 µL of sample. There is minimal hands-on sample preparation required and the assay is suitable for routine use in a clinical laboratory.
authors.affiliation: Department of Clinical Biochemistry, University Hospital South Manchester NHS Foundation Trust, Manchester, UK Manchester Academic Health Science Centre, University Hospital South Manchester, The University of Manchester, Manchester, UK Jo.adaway@uhsm.nhs.uk.
authors.forename: Joanne E
authors.initials: JE
authors.lastname: Adaway
authors.affiliation: Institute of Clinical Chemistry and Laboratory Medicine, University Hospital Carl Gustav Carus, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany.
authors.forename: Mirko
authors.initials: M
authors.lastname: Peitzsch
authors.affiliation: Department of Clinical Biochemistry, University Hospital South Manchester NHS Foundation Trust, Manchester, UK Manchester Academic Health Science Centre, University Hospital South Manchester, The University of Manchester, Manchester, UK.
authors.forename: Brian G
authors.initials: BG
authors.lastname: Keevil
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods; D006801:Humans; D008676:Metanephrine / Q000097:blood*; D052616:Solid Phase Extraction / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D008676:Metanephrine
keywords: 3-methoxytyramine; LC-MS/MS; Metanephrine; normetanephrine; online solid phase extraction; phaeochromocytoma