Evaluation of diffusion for inorganic-nitrogen analysis of natural water and wastewater

S. A. Khan, R. L. Mulvaney, K. Strle, B. P. Horgan

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11 Scopus citations


Public concern that agricultural use of N fertilizers may have adverse effects on environmental quality and human health has led to a growing need for reliable data concerning the concentration of inorganic N in ground and surface water. A study was conducted to compare the accuracy and precision of simple Mason-jar diffusion methods for quantitative determination of NH4/+ and NO3/- in a wide variety of water and wastewater, relative to colorimetry, ion-selective potentiometry, and steam distillation. Good agreement among methods was generally obtained with standard solutions prepared using deionized water; however, substantial differences often were observed with natural and anthropogenic samples, because of either Cl- interference in measurements with the NO3/- electrode or CO3/2- interference in distillation. Analytical accuracy also was evaluated by measuring recovery of N added as (NH4)2SO4 or KNO3 (6 mg N L-1). With most of the samples studied, quantitative recovery (97-103%) was not achieved by potentiometry or distillation. Quantitative recoveries usually were achieved by a manual Berthelot method for colorimetric determination of NH4/+, whereas recovery was often incomplete when NO3/- analyses were performed with an automated flow-injection system using Cd2+ reduction. Regardless of the sample matrix, diffusion was always accurate in measuring recovery of NH4/+ or NO3/-.

Original languageEnglish (US)
Pages (from-to)1890-1895
Number of pages6
JournalJournal of Environmental Quality
Issue number6
StatePublished - 2000


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