Simultaneous Determination of Anions and Cations by Multimodal Liquid Chromatography

A new method has been established for simultaneous determination of anions and cations in fertilizer sample by multimodal liquid chromatography with direct conductivity detection. An Acclaim Trinity P1 column based on nanopolymer silica hybrid technology with multimodal separation functional groups reversed-phase/anion-exchange/cation-exchange was used for the analysis. The chromatographic conditions were optimized and the effect ion of eluent on retention was discussed. Eight ions (Li+, NH4+, K+, HCOO-, NO2-, Cl-, NO3- and Br-) were separated and determined simultaneously by using 25 mmol/L CH3COONa solution containing 50% acetonitrile at pH = 5.0 as mobile phase. The flow rate was 0.50 mL/min and the temperature was 30 degrees C. Under the optimum conditions, the linear ranges of the method were in the range of 0.5-200 mg/L for all the ions with correlation coefficient of 0.9997-0.9999. Whereas the detection limits (S/N = 3) were in the range of 0.16-1.72 mg/L and the relative standard deviations (RSD, n = 9) were in the range of 1.3-2.5%. The method was applied to the determination of anions and cations in the fertilizer samples with satisfied results and the recoveries were in the range of 95.8%-103.8%.