title: Precise determination of dissolved silica in seawater by ion-exclusion chromatography isotope dilution inductively coupled plasma mass spectrometry.
abstract: Ion exclusion chromatograph (IEC) isotope dilution (ID) inductively coupled plasma mass spectrometry (ICP-MS) (IEC-ID-ICP-MS) was developed for measurement of dissolved silica in seawater, which was applied to production of certified reference materials (CRMs) of three concentration levels of nutrients (high, medium and low levels). IEC-ICP-MS has been employed to separate dissolved silica from seawater matrix. In the present study, in order to solve substantial problems due to spectral interference in ICP-MS and to improve the accuracy of IEC-ICP-MS beyond standard addition or conventional calibration methods, ID method was coupled with ICP-sector field mass spectrometry (operated under medium resolution,i.e., m/Δm=4000). In addition, effects of various operating parameters in ICP-MS on a silicon background level were also investigated to obtain lower background equivalent concentration (BEC). As a result, 3 ng g(-1) of the BEC and 0.5 % of relative standard uncertainties were achieved in the analyses of dissolved silica in seawater samples at concentration levels from 4.0 mg kg (-1) to 0.8 mg kg(-1) as silicon. The developed method was successfully validated by analyses of an artificial seawater containing a known amount of silicate and the seawater certified reference material MOOS-2 produced by the National Research Council Canada.
authors.affiliation: National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8563, Ibaraki, Japan. Electronic address: naoko-nonose@aist.go.jp.
authors.forename: Naoko
authors.initials: N
authors.lastname: Nonose
authors.affiliation: National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8563, Ibaraki, Japan.
authors.forename: Chikako
authors.initials: C
authors.lastname: Cheong
authors.affiliation: National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8563, Ibaraki, Japan.
authors.forename: Yukari
authors.initials: Y
authors.lastname: Ishizawa
authors.affiliation: National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8563, Ibaraki, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Miura
authors.affiliation: National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8563, Ibaraki, Japan.
authors.forename: Akiharu
authors.initials: A
authors.lastname: Hioki
mesh_terms: D002850:Chromatography, Gel / Q000379:methods / Q000592:standards*; D002852:Chromatography, Ion Exchange / Q000379:methods / Q000592:standards; D012623:Seawater / Q000032:analysis* / Q000737:chemistry; D012822:Silicon Dioxide / Q000032:analysis* / Q000737:chemistry; D013054:Spectrophotometry, Atomic / Q000379:methods / Q000592:standards*
chemical_list: D012822:Silicon Dioxide
keywords: Background equivalent concentration; Dissolved silica in seawater; Ion exclusion chromatograph; Isotope dilution