Single Column Ion Chromatography: I. Analysis of Inorganic Anions in Soils

Abstract

AbstractA useful analytical method is described for the determination of inorganic mono‐and divalent anions in soils. Single column ion chromatography (SCIC) is a rapid, sensitive, and precise method which can simultaneously detect Cl−, NO−2, NO−3, SO2−3, and SO2−4 in soils in less than 10 min. In addition, Br−, I−, and ClO−4 can be separated within 15 min. The method can be carried out on a commercially available HPLC instrument, using a 500 µL aliquot of soil extract and an eluent stream of 4 mM phthalic acid (pH 4.5). The inorganic anions are separated on a low‐capacity anion exchange column and quantified by conductimetric detection. Results obtained by the SCIC method agree closely with those obtained by other analytical methods: Cl−, AgNO3 titrimetric method (r = 0.987***); NO−2‐N, diazonium coupling reaction (r = 0.993***); NO−3‐N, steam distillation (r = 0.998***); SO2−4‐S, autoanalyzer (r = 0.998***). Using a 500 µL loop, SCIC detection limits, expressed in mg/L of soil extract, were: Cl−, Br−, NO−3‐N, and SO2−4‐S (0.025), ClO−4 and I− (0.5); NO−2‐N and SO2−3‐S (1.0). Several extracting reagents (water, LiCl, KCl, Ca[C2H3O2l2, and CaCl2) were compared to determine the best soil extraction procedure. This method proved to be reproducible as evident by the low CV values ranging from 3.6 to 8.4%. Notable advantages of this technique include: (i) single column simplicity, (ii) application to a wide variety of inorganic anions, (iii) simultaneous determination of ions in soil extracts without interferences by soil constituents, and (iv) inherent sensitivity greater than most methods employed for the determination of inorganic soil anions.