title: Improved method to measure urinary alkoxyacetic acids.
abstract: OBJECTIVE
  To simplify the current preparation of samples, and to improve the specificity and reliability of the conventional analytical methods to measure urinary alkoxyacetic acids.
  
  
  METHODS
  Samples containing alkoxyacetic acids including methoxy, ethoxy, and butoxyacetic acids (MAA, EAA, and BAA) were acidified with HCl and extracted with a mixed solvent of methylene chloride and isopropyl alcohol, then analysed by gas chromatography/mass spectrometry (GC/MS).
  
  
  RESULTS
  Optimal results were obtained when pH was 1.05-1.45, the ratio of methylene chloride and isopropyl alcohol was 2:1, and when extraction time was 10 minutes. Over the concentration range 0.3-200 micrograms/ml, MAA, EAA, and BAA could be determined with a pooled coefficient of variation (nine concentrations, six replicate samples) of 5.55%, 6.37%, and 6.41%, respectively. Urine samples were stable for at least 5 months and 3 freeze-thaw cycles at -20 degrees C. The limits of detection of MAA, EAA, and BAA were 0.055, 0.183, and 0.009 microgram/ml, respectively. The matrix effect of urine samples was negligible for MAA and EAA, but were marginally significant for BAA. The average recoveries of alkoxyacetic acids were 99%-101%. In urine samples MAA from 15 exposed workers showed a strong linear correlation (r = 0.999, slope = 1.01) between the new GC/MS method and Sakai's GC method.
  
  
  CONCLUSIONS
  The simplified non-derivatisation pretreatment of samples coupled with GC/MS can provide a specific, sensitive, simple, safe, and reliable method for the biological monitoring of occupational exposure of ethylene glycol ethers.
authors.affiliation: Institute of Occupational Safety and Health, Council of Labor Affairs, Taipei, Taiwan, Republic of China. stone@mail.cla.gov.tw
authors.forename: T S
authors.initials: TS
authors.lastname: Shih
authors.forename: J S
authors.initials: JS
authors.lastname: Chou
authors.forename: C Y
authors.initials: CY
authors.lastname: Chen
authors.forename: T J
authors.initials: TJ
authors.lastname: Smith
mesh_terms: D000085:Acetates / Q000652:urine*; D004784:Environmental Monitoring / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D006016:Glycolates / Q000652:urine; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016273:Occupational Exposure; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods
chemical_list: D000085:Acetates; D006016:Glycolates; C017095:n-butoxyacetic acid; C034096:ethoxyacetic acid; C013598:methoxyacetic acid