Determination of common inorganic anions and cations by non-suppressed ion chromatography with column switching

An ion chromatography (IC) method has been proposed for the determination of seven common inorganic anions (F−, H2PO4−, NO2−, Cl−, Br−, NO3−, and SO42−) and/or five common inorganic cations (Na+, NH4+, K+, Mg2+, and Ca2+) using a single pump, a single eluent and a single detector. The present system used cation-exchange and anion-exchange columns connected in series via a single 10-port switching valve. The 10-port valve was switched for the separation of either cations or anions in a single chromatographic run. When 1.0 mM trimellitic acid (pH 2.94) was used as the eluent, the seven anions and the five cations could be separated on the anion-exchange column and the cation-exchange column, respectively. The elution order was found to be F− < H2PO4− < NO2− < Cl− < Br− < NO3− < SO42− for the anions and Na+ < NH4+ < K+ < Mg2+ < Ca2+ for the cations. Complete separation of the above anions or cations was demonstrated within 35 min each. Detection limits calculated at S/N = 3 were 0.05–0.58 ppm (mg/l) for the anions and 0.05–0.38 ppm for the cations, whereas repeatability values were below 2.26, 2.76, and 2.90% for peak height, peak area and retention time, respectively. The method was successfully applied to the determination of inorganic anions and cations in river water samples.