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. (c) 2008 Elsevier B.V. All rights reserved.