Ion-exclusion/cation-exchange Chromatography with Dual Detection of the Conductivity and Spectrophotometry for the Simultaneous Determination of Common Inorganic Anionic Species and Cations in River and Wastewater
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Simultaneous determinations of common inorganic anionic species (SO_4^<2−>, Cl^−, NO_3^−, phosphate and silicate) and cations (Na^+, NH_4^+, K^+, Mg^<2+> and Ca2+) were conducted using an ion-chromatography system with dual detection of conductivity and spectrophotometry in tandem. The separation of ionic species on a weakly acidic cation-exchange resin was accomplished using a mixture of 100 mM ascorbic acid and 4 mM 18-crown-6 as an acidic eluent (pH 2.6), after which the ions were detected using a conductivity detector. Subsequently, phosphate and silicate were analyzed based on derivatization with molybdate and spectrophotometry at 700 nm. The detection limits at S/N = 3 ranged from 0.11 to 2.9 μM for analyte ionic species. This method was applied to practical river water and wastewater with acceptable criteria for the anion-cation balance and comparisons of the measured and calculated electrical conductivity, demonstrating the usefulness of the present method for water quality monitoring.