DETERMINATION OF ANIONS IN CERTIFIED REFERENCE MATERIALS BY ION CHROMATOGRAPHY

Certified reference materials (CRMs) which can be used to analyze anio ns in aqueous solution were prepared. Using ion chromatography, highly concentrated CRM solutions containing seven different anions (F-, Cl- , NO2-, NO3-, Br-, PO43-, and SO42-, 100 mg kg(-1) each) could be dire ctly separated without making any diluted solutions. To obtain optimiz ed separation conditions in this highly concentrated sample solution, a number of experiments including change of eluent composition and flo w-rate of the eluents and injection volumes were attempted. The best r esults 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 ml min(-1) as flow-rate and a 5 mu l sample loop. The resolution value reached to 1.5, which i s sufficient for quantitative analysis and all of seven different anio ns were perfectly separated within 15 min. (C) 1998 Elsevier Science B .V. All rights reserved.