Simultaneous Determination of Nitrate, Chloride, Sulfate, and Phosphate in Natural Waters by Ion Chromatography1
- M. A. Tabatabai and
- W. A. Dick2
Simultaneous 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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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