Sequential determination of nitrate and nitrite in natural waters by flow injection analysis

Authors

  • Josephine M. Castañares Institute of Chemistry, University of the Philippines, Diliman, Quezon City
  • Florian R. Del Mundo Institute of Chemistry, University of the Philippines, Diliman, Quezon City

DOI:

https://doi.org/10.26534/kimika.v11i1.9-17

Keywords:

FIA, homogeneous reduction, sequential determination, nitrate and nitrite, natural waters

Abstract

Nitrate is reduced to nitrite by hydrazine sulfate and catalyzed by Cu2+ under alkaline conditions at an elevated temperature of 75°C. The intensely colored azo derivative which is formed upon reaction with a mixed reagent of 3-nitroaniline and N-(1-naphthyl)ethylenediamine dihydrochloride (NED) is used as basis for the flow injection analysis (FIA) simultaneous determination of nitrate and nitrite using spectrophotometric detection.

A simplex-aided optimization was used to fmd the best ratio of mixed reagents to be used in the single detection of these anions. Good signal enhancement, ca. 240% (nitrate) and (400 %) nitrite were achieved in a minimum number of 15-20 experimental trials. The development of the FIA manifold for the simultaneous detection were then based from these optimized individual manifolds.

The method showed a wide linear range of 0-5.0 mg NO3- - N/L, 0 - 0.9 mg NO2- - N/L, and detection limits of 30 and 10 µg/L nitrate-nitrogen and nitrite-nitrogen respectively, with a sampling frequency of 80 determinations per hour. Interferences due to calcium and magnesium ions were removed on-line by a cation-exchange column.

Applications of the developed FIA method to lake, river and seawater were in good agreement with standard batch methods (r = 0.9986) which uses copper coated cadmium granules for the reduction step and sulfanilamide-NED as diazo-coupling reagents.

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How to Cite

Castañares, J. M., & Del Mundo, F. R. (1995). Sequential determination of nitrate and nitrite in natural waters by flow injection analysis. KIMIKA, 11(1), 9–17. https://doi.org/10.26534/kimika.v11i1.9-17

Issue

Vol. 11 (1995)

Section

Research Articles

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