Determination of anions in certified reference materials by ion chromatography

Certified reference materials (CRMs) which can be used to analyze anions in aqueous solution were prepared. Using ion chromatography, highly concentrated CRM solutions containing seven different anions (F^-, Cl^-, NO₂^-, NO₃^-, Br^-, PO₄^3-, and SO₄^2-, 100 mgkg^-1 each) could be directly separated without making any diluted solutions. To obtain optimized separation conditions in this highly concentrated sample solution, a number of experiments including change of eluent composition and flow-rate of the eluents and injection volumes were attempted. The best results were observed when a mixture of 2.0 mM Na₂CO₃ and 2.5 mM NaHCO₃ as an eluent was used with conditions of 0.5 mlmin^-1 as flow-rate and a 5 μl sample loop. The resolution value reached to 1.5, which is sufficient for quantitative analysis and all of seven different anions were perfectly separated within 15 min. Copyright (C) 1998 Elsevier Science B.V.