title: A revised method for determination of dialkylphosphate levels in human urine by solid-phase extraction and liquid chromatography with tandem mass spectrometry: application to human urine samples from Japanese children.
abstract: OBJECTIVE
  Biological monitoring of organophosphorus insecticide (OP) metabolites, specifically dialkylphosphates (DAP) in urine, plays a key role in low-level exposure assessment of OP in individuals. The aims of this study are to develop a simple and sensitive method for determining four urinary DAPs using high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS), and to assess the concentration range of urinary DAP in Japanese children.
  
  
  METHODS
  Deuterium-labeled DAPs were used as internal standards. Urinary dimethylphosphate (DMP) and diethylphosphate (DEP), which passed through the solid-phase extraction (SPE) column, and dimethylthiophosphate (DMTP) and diethylthiophosphate (DETP), which were extracted from a SPE column using 2.5 % NH3 water including 50 % acetonitrile, were prepared for separation analysis. The samples were then injected into LC-MS/MS. The optimized method was applied to spot urine samples from 3-year-old children (109 males and 116 females) living in Aichi Prefecture in Japan.
  
  
  RESULTS
  Results from the validation study demonstrated good within- and between-run precisions (<10.7 %) with low detection limits (0.4 for DMP and DMTP, 0.2 for DEP and 0.1 μg/L for DETP). The geometric mean values and detection rates of the urinary DAPs in Japanese children were 14.4 μg/L and 100 % for DMP, 5.3 μg/L and 98 % for DMTP, 5.5 μg/L and 99 % for DEP, and 0.6 μg/L and 80 % for DETP, respectively.
  
  
  CONCLUSIONS
  The present high-throughput method is simple and reliable, and can thereby further contribute to development of an exposure assessment of OP. The present study is the first to reveal the DAP concentrations in young Japanese children.
authors.affiliation: Department of Pathophysiological Laboratory Sciences, Field of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, 461-8673, Japan, ueyama.jun@e.mbox.nagoya-u.ac.jp.
authors.forename: Jun
authors.initials: J
authors.lastname: Ueyama
authors.forename: Isao
authors.initials: I
authors.lastname: Saito
authors.forename: Ayuko
authors.initials: A
authors.lastname: Takaishi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nomura
authors.forename: Mai
authors.initials: M
authors.lastname: Inoue
authors.forename: Aya
authors.initials: A
authors.lastname: Osaka
authors.forename: Yuka
authors.initials: Y
authors.lastname: Sugiura
authors.forename: Yumi
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Shinya
authors.initials: S
authors.lastname: Wakusawa
authors.forename: Hiroko
authors.initials: H
authors.lastname: Ogi
authors.forename: Kimio
authors.initials: K
authors.lastname: Inuzuka
authors.forename: Michihiro
authors.initials: M
authors.lastname: Kamijima
authors.forename: Takaaki
authors.initials: T
authors.lastname: Kondo
mesh_terms: D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D007306:Insecticides / Q000302:isolation & purification / Q000652:urine*; D007564:Japan; D008297:Male; D010755:Organophosphates / Q000302:isolation & purification / Q000652:urine*; D009943:Organophosphorus Compounds / Q000302:isolation & purification / Q000652:urine; D052616:Solid Phase Extraction; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D007306:Insecticides; D010755:Organophosphates; D009943:Organophosphorus Compounds; C034789:diethyl phosphate; C007477:dimethyl phosphate