title: Measurement of 1- and 3-methylhistidine in human urine by ultra performance liquid chromatography-tandem mass spectrometry.
abstract: BACKGROUND
  Determination of 1-methylhistidine (1-MH) and 3-methylhistidine (3-MH) is important to monitor muscle protein catabolism. Here, an ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for quantification of 1-MH and 3-MH in human urine is described.
  
  
  METHODS
  Urine samples were prepared by dilution with water after addition of isotopic internal standard. The samples were chromatographed on a SB-aq (2.1×50 mm, 1.8 μm) column with acetonitrile -0.1% formic acid in water (2:98, v/v) as mobile phase. Mass spectrometric detection was performed on a triple quadrupole mass spectrometer using positive electrospray ionization (ESI). 1-MH and 3-MH were monitored by the following transitions: 1-MH, m/z 170.1→ m/z 126.1; 3-MH, m/z 170.1→ m/z 124.1.
  
  
  RESULTS
  For 1-MH and 3-MH, calibration curves were linear over the concentration range of 5-500 nmol/ml. The lower limit of quantification was 5 nmol/ml. The accuracy was within 85%-115% and precision was <15%. 1-MH and 3-MH were proved to be stable under different storage and processing conditions. In addition, the detection was independent of matrix effect.
  
  
  CONCLUSIONS
  This rapid and specific UPLC/MS-MS method is suitable for the determination of urinary 1-MH and 3-MH.
authors.affiliation: Clinical Pharmacology Research Center, Peking Union Medical College Hospital and Chinese Academy of Medical Science, Beijing, PR China. wanghongyunpumc@sohu.com
authors.forename: Hongyun
authors.initials: H
authors.lastname: Wang
authors.forename: Pei
authors.initials: P
authors.lastname: Hu
authors.forename: Ji
authors.initials: J
authors.lastname: Jiang
mesh_terms: D000328:Adult; D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods*; D006801:Humans; D006868:Hydrolysis; D057230:Limit of Detection; D008762:Methylhistidines / Q000652:urine*; D012015:Reference Standards; D012016:Reference Values; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D008762:Methylhistidines; C028120:1-methylhistidine; C028118:3-methylhistidine