title: Simultaneous separation of common mono- and divalent cations on an acid-treated silica gel column by ion chromatography with indirect photometric detection and tyramine-oxalic acid, containing 18-crown-6 as eluent.
abstract: The application of unmodified silica gel (Super Micro Bead Silica Gel B-5, SMBSG B-5) as cation-exchange stationary phase in ion chromatography with indirect photometric detection for common mono- and divalent cations (Li+, Na+, NH4+, K+, Mg2+ and Ca2+) was carried out using 0.75 mM tyramine [4-(2-aminoethyl)phenol]-0.25 mM oxalic acid at pH 5.0 as the eluent. Although complete group separation between these mono- and divalent cations was achieved on the SMBSG B-5 column (150x4.6 mm I.D.) in 12 min, peak shapes of NH4+ and K+ were strongly tailed. Hence, the application of SMBSG B-5 silica gel treated with conc. hydrochloric acid at reflux-temperature for 12 h for the simultaneous separation of these cations was carried out. Although the retention volumes of these cations decreased on the acid-treated SMBSG B-5 silica gel column, the peak shapes of NH4+ and K+ were quite improved. Excellent simultaneous separation and highly sensitive detection at 275 nm [detection limits (signal-to-noise ratio of 3 and injection volume of 20 microl), 0.34 microM for Li+, 0.47 microM for Na+, 0.39 microM for NH4+, 0.59 microM for K+, 0.24 microM for Mg2+ and 0.28 microM for Ca2+] were achieved in 15 min on the acid-treated SMBSG B-5 column using 0.5 mM tyramine-0.2 mM oxalic acid-10 mM 18-crown-6 (1,4,7,10,13,15-hexaoxacyclooctadecane) at pH 5.5 as the eluent.
authors.affiliation: Ceramics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Japan. kazu.ohta@aist.go.jp
authors.forename: Kazutoku
authors.initials: K
authors.lastname: Ohta
authors.forename: Keiji
authors.initials: K
authors.lastname: Kusumoto
authors.forename: Yasumasa
authors.initials: Y
authors.lastname: Takao
authors.forename: Atsuya
authors.initials: A
authors.lastname: Towata
authors.forename: Hisashi
authors.initials: H
authors.lastname: Morikawa
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Ohashi
mesh_terms: D002413:Cations, Divalent / Q000302:isolation & purification*; D002414:Cations, Monovalent / Q000302:isolation & purification*; D002853:Chromatography, Liquid / Q000379:methods*; D043844:Crown Ethers; D004988:Ethers, Cyclic / Q000737:chemistry*; D019815:Oxalic Acid / Q000737:chemistry*; D012680:Sensitivity and Specificity; D058428:Silica Gel; D012822:Silicon Dioxide; D013056:Spectrophotometry, Ultraviolet / Q000379:methods*; D014439:Tyramine / Q000737:chemistry*
chemical_list: D002413:Cations, Divalent; D002414:Cations, Monovalent; D043844:Crown Ethers; D004988:Ethers, Cyclic; D058428:Silica Gel; C015762:18-crown-6; D012822:Silicon Dioxide; D019815:Oxalic Acid; D014439:Tyramine