Counterionic Detection by ICP-AES for Determination of Inorganic Anions in Water Elution Ion Chromatography Using a Zwitterionic Stationary Phase

The analytical methods for the determination of inorganic anions by water elution ion chromatography using a zwitterionic column (C14SB-coated column) have been explored, where pure water was used as the mobile phase. In the present ion chromatography, the complicated peaks derived from various "ion pairs" appeared on the chromatogram when the sample solution contained several kinds of cations and anions. The chromatograms with the complicated peaks were simplified by using a preconditioning cation-exchange column. In the preconditioning column, various kinds of countercations of the analyte anions were converted to a particular kind of common cation, and thus all the analyte anions were separated as the common cation form. The more effective separation was achieved by converting to a divalent cation (Mg(2+)) form than a monovalent cation (Na(+)) form, because the anions paired with the divalent cation provided longer elution times than those paired with the monovalent cation. All the analyte anions separated as the common cation form were simply determined from their calibration curves drawn from conductivity detection. In addition, the counterionic determination of the anions was also attempted by using ICP-AES. The analyte anions were determined by measuring their countercations with ICP-AES, where the calibration curve of the countercation measured by ICP-AES could be used.