Simultaneous Determination of Nitrate, Chloride, Sulfate, and Phosphate in Natural Waters by Ion Chromatography

Abstract

AbstractSimultaneous analysis of anions in water samples is needed. Studies to evaluate the Dionex Model 10 Ion Chromatograph (IC) for simultaneous determination of NO3−, Cl−, SO42−, and PO43− in water samples, including soil extracts, showed that the results by the IC method agreed closely with those obtained by the steam‐distillation method for NO3−, colorimetric method using mercuric thiocyanate and ferric ammonium sulfate for Cl−, reduction and colorimetric determination as methylene blue for SO42−, and colorimetric molybdenum blue method for PO43−. The IC method is based on separation of the anions by a separator column containing Dionex low‐capacity anion‐exchange resin in the HCO3− form and on converting the various anions to their corresponding acids by a suppressor column containing a strong acid cation‐exchange resin in the H+ form. A solution 3.0 mM NaHCO3 + 2.4 nM Na2CO3 is used as the eluent, and electrical conductivity is used as the mode of detection. The method is precise and accurate, and can detect as little as 0.1 mg/L of NO3−‐N, Cl−, SO42−‐S, or PO43−‐P in water samples. The coefficient of variation ranged from 0.44 to 8.6% for NO3−‐N, from 0.14 to 4.3% for Cl−, from 0.13 to 1.1% for SO42−‐S, and from 0.55 to 8.6% for PO43−‐P. With the IC method, the 4 anions indicated can be determined simultaneously in 2 mL of water in approximately 10 min.