title: Evaluation of an ODS column modified with zwitterionic/nonionic mixed surfactants and its application to direct injection determination of inorganic anions.
abstract: An octadecylsilica (ODS) column modified with zwitterionic/nonionic mixed surfactants was evaluated for the direct injection determination of inorganic anions in biological fluids by ion chromatography. A zwitterionic surfactant (sulfobetaine-type) and a nonionic surfactant (polyoxyethylene-type) were used for a stationary-phase modification. When aqueous electrolyte solutions with concentrations of sub-mM to several mM were used as a mobile phase, the zwitterionic surfactant coated on the ODS surface exhibited unique separation selectivity for ionic species, while the nonionic surfactant coated on the ODS might have formed a hydrophilic network over the ODS surface and restricted matrix proteins from adsorbing on the stationary phase. Consequently, the mixed surfactant-modified column system allowed an efficient ion chromatographic separation of inorganic anions as well as a size-exclusive removal of column-fouling proteins. This separation system was applied to the direct injection determination of UV-absorbing anions in human saliva. The detection limits for nitrite, nitrate, iodide and thiocyanate were 3.1, 2.7, 4.5 and 25 microM, respectively, with UV detection at 210 nm (injection volume; 20 microl), and their relative standard deviations for 5 replicate measurements of saliva samples spiked with 100 microM each of those anions were 1.4, 0.9, 2.2 and 5.5%, respectively.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Hasegawa
authors.forename: Tomonari
authors.initials: T
authors.lastname: Umemura
authors.forename: Akira
authors.initials: A
authors.lastname: Koide
authors.forename: Koichi
authors.initials: K
authors.lastname: Chiba
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ueki
authors.forename: Kin-ichi
authors.initials: K
authors.lastname: Tsunoda
authors.forename: Hiroki
authors.initials: H
authors.lastname: Haraguchi
mesh_terms: D000838:Anions / Q000032:analysis* / Q000737:chemistry; D002845:Chromatography / Q000295:instrumentation* / Q000379:methods; D012822:Silicon Dioxide / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D000838:Anions; D013501:Surface-Active Agents; C026679:octadecylsilica; D012822:Silicon Dioxide