Ion Chromatographic Determination of Sulfate and Nitrate in Soils
1979
Dick, W. A. | Tabatabai, M. A.
A simple and precise ion chromatographic (IC) method for determination of SO₄²⁻ and NO₃⁻ in soils is described. It involves determination of these anions in soil extracts by using a Dionex Model 10 Ion Chromatograph. An aliquot (≃2 ml) of soil extract is injected in the eluent stream (3.0mM NaHCO₃ + 1.8mM Na₂CO₃), and the anions are separated by an analytical column containing Dionex low-capacity anion-exchange resin in the HCO₃⁻ form and converted to the corresponding acids by a suppressor column containing a strong acid cation-exchange resin in the H⁺ form. Conductivity is used as the mode of detection. Results of SO₄²⁻ and NO₃⁻ in soils by the IC method agreed closely with those obtained by the methylene blue and steam-distillation methods, respectively. Tests indicated that S²⁻, SO₃²⁻, S₂O₃²⁻, S₂O₅²⁻, S₄O₆²⁻, SCN⁻, thiourea, glucose-6-sulfate, and p-nitrophenyl sulfate do not interfere in determination of SO₄²⁻. Also, NO₂⁻ does not interfere in determination of NO₃⁻. This method gives quantitative recovery of SO₄-S and NO₃-N added to soils (5–50 µg/g soil). The detection limit is 1 µg SO₄-S or NO₃-N/g soil (0.2 µg SO₄-S or NO₃-N/ml of soil extract). With the IC method, SO₄-S and NO₃-N can be determined simultaneously in about 10 min.
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