Standard Test Method for Anions in Water by Suppressed Ion Chromatography

Abstract

5.1 Ion chromatography provides for both qualitative and quantitative determination of seven common anions, F−, Cl−, NO2−, HPO4−2, Br−, NO3−, and SO4−2, in the milligram per litre range from a single analytical operation requiring only a few millilitres of sample and taking approximately 10 min to 15 min for completion. Additional anions, such as carboxylic acids, can also be quantified. Note 2: This test method may be used to determine fluoride if its peak is in the water dip by adding 1 mL of eluent (at 100× the concentration in 8.3) to all 100 mL volumes of samples and standards to negate the effect of the water dip. (See 6.3, and also see 6.4.) The quantitation of unretained peaks should be avoided. Anions such as low molecular weight organic acids (formate, acetate, propionate, etc.) that are conductive coelute with fluoride and would bias fluoride quantitation in some drinking waters and most wastewaters. The water dip can be further minimized if measures are taken to remove carbonic acid which remain in the eluent after suppression using carbonate based eluents. There is no water dip if hydroxide eluents are used. 5.2 Anion combinations such as Cl−/Br− and NO2−/NO3−, which may be difficult to distinguish by other analytical methods, are readily separated by ion chromatography.