SIMULTANEOUS DETERMINATION OF ANIONS AND CATIONS IN ENVIRONMENTAL SAMPLES BY USING A WEAKLY ACIDIC CATION-EXCHANGE COLUMN WITH 2,6-PYRIDINEDICARBOXYLIC ACID, SULFOSALICYLIC ACID, AND 18-CROWN-6 AS ELUENT

Abstract

Weakly acidic cation exchange resin can be used for simultaneous separation of anions and cations when acidic eluents were employed. On the weakly acidic cation exchange resin, anions were retained by ion exclusion mechanism, while cations by cation exchange mechanism. The selection of eluent is very important for the separation of interesting analytes. In this study, a mixture of 0.6 mmol/L 2,6-pyridinedicarboxylic acid (PDCA), 0.75 mmol/L sulfosalicylic acid (SSA), and 6.0 mmol/L 18-crown-6 was employed as eluent for the simultaneous separation of common inorganic anions (Cl−, NO3 − and SO4 2−) and cations (Na+, NH4 +, K+, Mg2+, and Ca2+). A good separation of these anions and cations on the weakly acidic cation exchange column (Tosoh TSKgel OApak-A) was achieved in 16 min. The linear range of peak area calibration curves for all analytes were up to two orders of magnitude. The conductivity detection limits calculated at S/N=3 were from 0.2 to 1.6 μmol/L for anions and cations. The method developed in this work was successfully applied to the simultaneous determination of major inorganic anions and cations in several environmental water samples.