title: Identification of the source of reagent variability in the xanthydrol/urea method.
abstract: Contamination of food and food packaging material by rodent urine is evidence of insanitary conditions. Urea from rodent urine is used as a chemical indicator of contamination. The limit of detection of the xanthydrol/urea AOAC Method 959.14 by formation of dixanthylurea crystals is 4 micrograms urea isolated from urine on packaging material. Six different lots of xanthydrol from 5 different manufacturers were compared. Differences in urea detection sensitivity of the xanthydrol of up to 1000-fold were observed. Melting points showed further evidence of variability and impurities in xanthydrol lots. A liquid chromatographic method was developed to separate and identify the impurities. Confirmation of analytes was performed by gas chromatography/mass spectrometry.
authors.affiliation: U.S. Food and Drug Administration, Division of Natural Products, Washington, DC 20204, USA.
authors.forename: P V
authors.initials: PV
authors.lastname: Biles
authors.forename: G C
authors.initials: GC
authors.lastname: Ziobro
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid; D003460:Crystallization; D005504:Food Analysis; D005506:Food Contamination; D018857:Food Packaging; D008401:Gas Chromatography-Mass Spectrometry; D007202:Indicators and Reagents; D012377:Rodentia / Q000652:urine*; D012680:Sensitivity and Specificity; D014508:Urea / Q000032:analysis*; D014966:Xanthenes / Q000592:standards*
chemical_list: D007202:Indicators and Reagents; D014966:Xanthenes; C009690:xanthydrol; D014508:Urea