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 liter range from a single analytical operation requiring only a few milliliters of sample and taking approximately 10 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 one 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.

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.

1.1 This test method covers the sequential determination of fluoride, chloride, nitrite, ortho-phosphate, bromide, nitrate, and sulfate ions in water by suppressed ion chromatography.

Note 1—Order of elution is dependent upon the column used; see Fig. 1.