title: A simple and rapid in situ preconcentration method for trace ammonia nitrogen in environmental water samples using a solid-phase extraction followed by spectrophotometric determination.
abstract: A simple and rapid in situ preconcentration method for the spectrophotometric determination of trace ammonia nitrogen in environmental water samples has been developed based on solid-phase extraction using a small column packed with octadecyl group-bonded silica gel (Sep-Pak C18 cartridge). A water sample was taken into a graduated syringe for easy and simple operation and prevention of contamination immediately after sample collection. Ammonia in the sample was reacted with hypochlorite and thymol to be converted into indothymol blue; then the formed indothymol blue was collected as an ion pair between indothymol blue and tetrabutylammonium ion on a Sep-Pak C18 cartridge. The indothymol blue on the cartridge was stable for 4 days. The retained indothymol blue was easily eluted with a mixture of methanol and 0.01 mol/l sodium hydroxide solution. The color intensity due to the indothymol blue was spectrophotometrically measured at 725 nm. The proposed method was successfully applied to environmental water samples such as river water.
authors.affiliation: Department of Material Science, Interdisciplinary Faculty of Science and Engineering, Shimane University, Matsue, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Okumura
authors.forename: Sachiko
authors.initials: S
authors.lastname: Honda
authors.forename: Kaoru
authors.initials: K
authors.lastname: Fujinaga
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Seike
mesh_terms: D000641:Ammonia / Q000737:chemistry* / Q000378:metabolism; D004784:Environmental Monitoring / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry*; D009584:Nitrogen / Q000032:analysis*; D013053:Spectrophotometry / Q000379:methods; D013943:Thymol / Q000737:chemistry / Q000378:metabolism; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D013943:Thymol; D000641:Ammonia; D009584:Nitrogen