Ion Chromatographic Determination of Sulfate and Nitrate in Soils

Abstract

AbstractA 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.