ASTM D4327-17

5.1 Ion chromatography provides for both qualitative and quantitative determination of seven common anions, F⁻, Cl⁻, NO₂⁻, HPO_{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.

1.1 This test method2^,3 covers the sequential determination of fluoride, chloride, nitrite, Note 1: Order of elution is dependent upon the column used; see Fig. 1.

1.3 It is the user's responsibility to ensure the validity of this test method for other matrices.

1.4 Concentrations as low as 0.01 mg/L were determined depending upon the anions to be quantified, in single laboratory work. Utilizing a 50-μL sample volume loop and a sensitivity of 3000 μS/cm full scale, the approximate detection limits shown in Table 1 can be achieved. Lower detection limits have been observed with newer instrumentation, column technology and eluents. The analyst must assure optimum instrument performance to maintain a stable baseline at more sensitive conductivity full-scale settings.