Simultaneous separation of common mono- and divalent cations on a calcinated silica gel column by ion chromatography with indirect photometric detection and aromatic monoamines-oxalic acid, containing crown ethers, used as eluent.
The application of unmodified silica gel (Super Micro Bead Silica Gel B-5, SMBSG B-5) as a cation-exchange stationary phase in ion chromatography with indirect photometric detection (IC-IPD) for the separation of common mono- and divalent cations (Li+, Na+, NH4+, K+, Mg2+ and Ca2+) was carried out using various aromatic monoamines [tyramine [4-(2-aminoethyl)phenol], benzylamine, phenylethylamine, 2-methylpyridine and 2,6-dimethylpyridine] as eluents. When using these amines as eluents, the peak resolution between these mono- and divalent cations was not quite satisfactory and the peak shapes of NH4+ and K+ were largely destroyed on the SMBSG B-5 silica gel column. Hence, the application of SMBSG B-5 silica gel calcinated at 200, 400, 600, 800 and 1000 degrees C for 5 h in the IC-IPD was carried out. The peak shapes of the monovalent cations were greatly improved with increasing calcination temperature and, as a result, symmetrical peaks of these mono- and divalent cations were obtained on the SMBSG B-5 silica gel calcinated at 1000 degrees C as the stationary phase. In contrast, the peak resolution between these mono- and divalent cations was not improved. Therefore, crown ethers [18-crown-6 (1,4,7,10,13,15-hexaoxacyclooctadecane), 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane)] were added to the eluent for the complete separation of these mono- and divalent cations. Excellent simultaneous separation and highly sensitive detection at 275 nm were achieved in 25 min on a column (150x4.6 mm I.D.) packed with SMBSG B-5 silica gel calcinated at 1000 degrees C by elution with 0.75 mM tyramine-0.25 mM oxalic acid at pH 5.0 containing either 1.0 mM 18-crown-6 or 10 mM 15-crown-5.
Ohta
Kazutoku
K
Ceramics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Japan. kazu.ohta@aist.go.jp
Kusumoto
Keiji
K
Takao
Yasumasa
Y
Towata
Atsuya
A
Kawakami
Shoji
S
Murase
Yoshio
Y
Ohashi
Masayoshi
M
D000588:Amines / Q000737:chemistry*; D002413:Cations, Divalent / Q000302:isolation & purification*; D002414:Cations, Monovalent / Q000302:isolation & purification*; D002853:Chromatography, Liquid / Q000379:methods*; D004988:Ethers, Cyclic / Q000737:chemistry*; D019815:Oxalic Acid / Q000737:chemistry*; D010783:Photometry / Q000379:methods*; D058428:Silica Gel; D012822:Silicon Dioxide
D000588:Amines; D002413:Cations, Divalent; D002414:Cations, Monovalent; D004988:Ethers, Cyclic; D058428:Silica Gel; D012822:Silicon Dioxide; D019815:Oxalic Acid