Ion chromatography with indirect photometric detection of common mono- and divalent cations using an unmodified silica gel column and tyramine/oxalic acid/18-crown-6 as eluent Original Research Article

A separation column (150 mm × 4.6 mm i.d.) packed with an unmodified silica gel (Super Micro Bead Silica Gel B-5: SMBSG B-5) was applied to ion chromatography with indirect photometric detection (IC-IPD) for common mono- and divalent cations (Li+, Na+, NH4+, K+, Mg2+ and Ca2+) using tyramine (4-aminoethylphenol) as eluent. When using 0.5 mM tyramine/0.2 mM oxalic acid at pH 4.75 as the eluent, complete separation of the divalent cations and incomplete separation of the monovalent cations were achieved. On the addition of 3 mM 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) to the eluent, highly sensitive indirect-UV photometric detection at 275 nm and excellent separation for these cations were achieved in 17 min. The proposed IC-IPD was successfully applied to cation analysis in various natural water samples.