title: Coulometric titration of urea with electrogenerated hypobromite.
abstract: A definitive method is described for the indirect assay of several tens of milligrams of urea by coulometric titration. Urea was decomposed in concentrated sulfuric acid using a Kjeldahl flask. Subsequently, the formed ammonium ion was titrated with electrogenerated hypobromite ion in a sodium bromide-sodium tetraborate medium of pH 8.6, with amperometric end-point detection. Parameters affecting the pretreatment procedure were evaluated. The optimized conditions included the heating of 2 g of urea at around 300°C for 2 h with 10 cm(3) of sulfuric acid. Under the proposed conditions, the assay value with expanded uncertainty (k = 2), 99.870 ± 0.026%, agreed well with the certified value of NIST SRM 912a urea, 99.9 ± 0.1%.
authors.affiliation: Faculty of Engineering, Tokyo University of Science, Tokyo, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Kato
authors.forename: Takuma
authors.initials: T
authors.lastname: Koseki
authors.forename: Yukie
authors.initials: Y
authors.lastname: Aoki
authors.forename: Ayako
authors.initials: A
authors.lastname: Yamada
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D001959:Bromates / Q000737:chemistry*; D055664:Electrochemical Techniques; D014508:Urea / Q000032:analysis*
chemical_list: D001959:Bromates; D014508:Urea; C027664:hypobromous acid