Simultaneous ion chromatography of inorganic anions together with some organic anions and alkaline earth metal cations using chelating agents as eluents

Abstract

The possibility of the simultaneous separation of inorganic and some organic anions and alkaline earth metal cations was investigated on two silica gel-based anion exchangers with the chelating agent ethylenediaminetetraacetic acid (EDTA), 1,2-diaminocyclohexanetetraacetic acid (DCTA), ethylene glycol bis(2-aminoethyl ether) tetraacetic acid (EGTA) and diethylenetriaminopentaacetic acid (DTPA) as eluents. The retention times ( t R) of all the inorganic and organic anions decreased with increasing pH and concentration of the eluents, whereas for the alkaline earths the t R vs. pH plots were “bell-shaped”, which indicated that alkaline earths could be separated either as metal cations or as chelating anions, depending on the pH and concentration of the eluent, but with almost the same sequence Ba 2+, Sr 2+, Ca 2+, Mg 2+. Under the experimental conditions EDTA and DCTA were usually applicable for the simultaneous separation of inorganic and some organic anions and alkaline earth metal ions, whereas EGTA and DTPA were more suitable for inorganic and organic anions but not good for alkaline earth metal ions. The proposed method was used for the simultaneous determination of some inorganic and organic anions and alkaline earth metal ions in natural samples such as drinking water, mineral water, brine and spinach juice, with satisfactory results.