Simultaneous analysis of inorganic monovalent anions/cations using mixed-bed single-column ion chromatography

The ion-exchange properties of a new mixed-bed ion-exchange column Scherzo SSC18 (Imtakt, USA) were investigated. This mixed-mode column is packed with two types of 3 µm spherical silica particles having either octadecyl- and strong cation-exchange functional groups or octadecyl- and strong anion-exchange functional groups. The regularities of the retention of alkali metal cations and inorganic anions were studied with diluted acids (sulfuric, perchloric to phosphoric, nitric, oxalic and citric acids) as eluents and direct conductivity for the detection. Eluent concentration, column temperature and organic solvent addition effects were investigated. The separations were achieved on the basis of ion-exchange interactions introduced by the strong anion and strong cation-exchange functionalities of the stationary phase; meanwhile, contribution of hydrophobic interactions was also evident for the hydrophobic iodide and thiocyanate. The simultaneous separation of 12 inorganic anions and cations in 20 min was obtained under isocratic conditions with 1 mM oxalic acid as eluent. The applicability of developed method to the determination of chloride, sodium, potassium as well as nitrite, nitrate and ammonium in soil extracts was demonstrated with good potential for nitrogen speciation studies.