title: Detection of melamine in a human renal uric acid stone by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).
abstract: BACKGROUND
  The link between melamine-contaminated daily foodstuffs and urolithiasis formation has drawn an international concern. However, detection of melamine levels in urine may not completely represent external melamine exposure. Thus, finding an additional analytical method for the study of environmental melamine exposure and its adverse effect in humans is crucial.
  
  
  METHODS
  Eleven adult patients diagnosed with uric acid urolithiasis were retrospectively analyzed. Melamine levels in their overnight one-spot urine samples were measured by a triple quadrupole liquid chromatography tandem mass spectrometry (LC-MS/MS). The compositions of stone samples were analyzed by the Fourier transform infrared (FTIR) spectrophotometer and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).
  
  
  RESULTS
  Seven (63.6%) out of 11 patients had detectable melamine levels in their urine specimens (method of detection limit: 0.8 ng/ml). Three patients (27.3%) were highly suspected of having melamine-containing urolithiasis in FTIR spectra. In one of those three cases who still had available stored stone specimens, MALDI-TOF MS further confirmed melamine components in this male patient's stone specimens. In contrast, his urinary melamine level was below the detection limit by LC-MS/MS.
  
  
  CONCLUSIONS
  Direct analysis of melamine in the composition of urolithiasis by MALDI-TOF MS can be an additional analytical method to evaluate for external melamine exposure.
authors.affiliation: Department of Urology, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Chia-Chu
authors.initials: CC
authors.lastname: Liu
authors.forename: Chia-Fang
authors.initials: CF
authors.lastname: Wu
authors.forename: Jentaie
authors.initials: J
authors.lastname: Shiea
authors.forename: Yi-Tzu
authors.initials: YT
authors.lastname: Cho
authors.forename: Tusty-Jiuan
authors.initials: TJ
authors.lastname: Hsieh
authors.forename: Yii-Her
authors.initials: YH
authors.lastname: Chou
authors.forename: Bai-Hsiun
authors.initials: BH
authors.lastname: Chen
authors.forename: Shu-Pin
authors.initials: SP
authors.lastname: Huang
authors.forename: Wen-Jeng
authors.initials: WJ
authors.lastname: Wu
authors.forename: Jung-Tsung
authors.initials: JT
authors.lastname: Shen
authors.forename: Mei-Yu
authors.initials: MY
authors.lastname: Chang
authors.forename: Chun-Hsiung
authors.initials: CH
authors.lastname: Huang
authors.forename: Ai-Wen
authors.initials: AW
authors.lastname: Chang
authors.forename: Ming-Tsang
authors.initials: MT
authors.lastname: Wu
mesh_terms: D000328:Adult; D000368:Aged; D002853:Chromatography, Liquid; D004781:Environmental Exposure; D004785:Environmental Pollutants / Q000737:chemistry* / Q000633:toxicity / Q000652:urine; D005260:Female; D006801:Humans; D007669:Kidney Calculi / Q000737:chemistry* / Q000652:urine; D057230:Limit of Detection; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D017550:Spectroscopy, Fourier Transform Infrared; D053719:Tandem Mass Spectrometry; D014227:Triazines / Q000737:chemistry* / Q000633:toxicity / Q000652:urine; D014527:Uric Acid / Q000378:metabolism
chemical_list: D004785:Environmental Pollutants; D014227:Triazines; D014527:Uric Acid; C011907:melamine